We expose the bad advice that wastes your time and money.

Gregg Keizer- PC World - June 2004

Magnets zap your data.

For venerable floppies, this statement holds true.  We placed a 99-cent magnet on a 3.5-inch floppy for a few seconds.  The magnet stuck to the disk and ruined its data.

Fortunately, most modern storage devices, such as SD and Compact Flash memory cards, are immune to magnetic fields.  "There's nothing magnetic in flash memory, so [a magnet] won't do anything," says Bill Frank, executive director of the Compact Flash Association.  "A magnet powerful enough to disturb the electrons in flash would be powerful enough to suck the iron out of your blood cells," says Frank.

The same goes for hard drives.  The only magnets powerful enough to scrub data from a drive platter are laboratory degaussers or those used by government agencies to wipe bits off media.  "In the real world, people are not losing data from magnets," says Bill Rudock, a tech-support engineer with hard-drive maker Seagate.  "In every disk," notes Rudock, "there's one heck of a magnet that swings the head."

Want to erase data from a hard drive you plan to toss?  Don't bother with a magnet.  Overwrite the data that is stored on the media instead. For flash, fill up the drive with anything, like pictures of your beloved dachshund.  Unlike with magnetic media, from which experts can usually recover at least some overwritten data, once new data is written to flash media, the old data is gone forever.  To overwrite the contents of a hard drive, try Eraser from Heidi Computers.

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If you don't 'stop' a USB device before unplugging it from a PC, you'll screw things up.

When you unplug a USB device without first "stopping" it in Windows (accomplished by clicking the Remove Hardware icon in the taskbar), your PC makes a bing-bong sound and usually pops up a message scolding you for the move or warning that what you just did can delete data saved on USB storage devices or damage hardware.

We're cautious about unplugging a device while it's still writing data (an action USB flash-drive makers always warn against) because doing so can cause major damage.  Case in point: One PC World editor unplugged an external USB hard drive that was doing some activity in the background; he lost all his data and damaged the drive itself.

If you wait until the device stops writing data and then pull the drive out, you're unlikely to experience serious problems.  Although Windows takes you to task for such rashness, even Microsoft downplays the peril.  The company told us that any damage will "depend on the USB device, but in general [unplugging a USB peripheral] shouldn't affect the system."

To see if the task has negative effects, we unplugged and plugged a bunch of USB devices, including a camera, a printer, a USB flash drive, and a scanner, without first "stopping" them in Windows.  The only problem was Windows' failure to recognize our USB flash drive after we had unplugged it and then immediately plugged it in again.  If that happens to you, wait a few seconds between unplugging and plugging.  If that doesn't work, reboot Windows.  And if that doesn't work, run the Add Hardware wizard from the Control Panel to make Windows "see" the USB device.  For more on USB devices, visit USBMan.

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Cookies track everything you do on the Internet.

When cookies first appeared, some Web users got bent out of shape because they thought cookies would track their every move online. Wrong.

Sure, cookies can perform limited tracking when you're browsing Web pages.  And some persistent cookies can trace your movements from site to site.  For instance, cookies from Double-click, a company that feeds targeted Web ads to users, track your surfing to any Double-click-enabled site to make sure that you don't see the same advertisement over and over.

But most cookies are far less intrusive.  A cookie used by Amazon.com, for example, to personalize the Web site for you doesn't pay any attention to what you do when you head to another shopping site such as Barnes and Noble.

If you're worried about cookies, turn them off in your browser (although doing so will render many sites virtually unsurfable).  In IE, choose Tools, Internet Options, click the Privacy tab, and click Advanced to override automatic cookie handling.  Also, consider opting out of Double-clicks site-to-site cookie tracking.

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Terrible things happen if you turn off your PC without shutting down Windows.

Don't touch that switch!  According to Microsoft, if you turn off your PC without first shutting down Windows, your hard drive could become more fragmented, files could become corrupted, and you could lose data.

Maybe Microsoft's warning holds some water, but we wouldn't worry about straining the system or harming Windows.  We ran 30 iterations of an informal test, turning off a pair of systems running Windows XP without first shutting down Windows.  Each time we left documents open in Word, Outlook, and Quicken.  And we left our Internet connection up and running.

After we turned each PC back on, we ran Symantec's Norton Disk Doctor and the Windows disk checker to see if the hard drive had suffered any ill effects.  We reopened the applications that we had left running and reconnected to the Internet.

Problems?  Disk Doctor found no disk errors, and our files were intact--at least up to the last time they were saved, but not always to the point of the last edit made.  Outlook recovered without a glitch, and so did Quicken. (We didn't check disk fragmentation because some hard-drive experts told us that defragging today's faster, bigger drives has little to no effect on performance.)

If you're uneasy about just switching off the PC, change the Power Options settings.  From the Control Panel, open Power Options, click the Advanced tab, and under 'Power buttons' select Hibernate.  Now whenever you push the power button,  Windows will save itself in its current state.  Turn the computer on later, and Windows will pop up, just as you left it, in a lot less time than the system would take to boot.

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Opting out of spam gets you even more spam.

You've heard the advice.  Don't reply to spam.  If you do, you'll get even more because you've just told the spammer that your e-mail address is legit.

"No one has done a complete test of this because it's difficult, if not impossible, to prove beyond a doubt," says Ari Schwartz, associate director for the Center for Democracy & Technology.  With spam accounting for as much as 83 percent of all Internet-delivered messages in the United States, he says, "if you do opt out and get more spam, how will you know you wouldn't have received it anyway?"

Sometimes opting out does work.  Last year CDT researched spam sources by creating e-mail accounts, seeding them through various venues, noting the amount of spam that each account received, and opting out.  Many companies complied with the opt-out requests within two weeks.

"Knowing who to opt out from is key," says Schwartz. "Opting out of legitimate companies drops you off their lists, but when you do that with 'real' spammers, the results are unclear."

Regardless of whether you opt out, spammers have various tools to grab addresses.  You can't completely protect your inbox, but you can take defensive measures, such as keeping your e-mail address off public sites, says Schwartz.

If you're still looking for a good spam filter, try Cloudmark's SpamNet, or another program recommended in "Spam-Proof Your In-Box."

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Hackers can destroy data on your computer's hard drive.

"The MyDoom.f worm took a step back into an era where viruses actually attacked data," says Bryson Gordon, a senior manager with McAfee Security.  Although viruses and worms that attack files are relatively uncommon, they are nightmare number one for anyone connected to the Internet.

Among other nefarious activities, MyDoom.f sniffed around on infected PCs looking for Word, Excel, and graphics files and then randomly deleted some of what it found.  Of the people whose PCs got the worm, 40 percent lost Word files and 60 percent lost Excel files.

Today's hackers want to hijack systems, not destroy them.  Rather than wipe out data, worms and viruses want intact PCs to send spam or to attack Web sites. "Just like a biological virus, if a computer virus kills the host before it propagates, it can't propagate," says Allen Householder, an Internet security analyst with the U.S. Computer Emergency Response Team, which is now part of the Department of Homeland Security.

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Turning off your PC daily to save power shortens its life.

Here's a topic that provokes debate.  One side argues that turning the PC on and off stresses components.  The other side says it's a good thing; even the best programs and the OS can get cranky without occasional shutdowns.

There's no definitive answer.  Most authorities, however, lean toward the idea that shutting off does more good than harm--plus it saves power. Kevin Krewell, editor in chief of the Microprocessor Report, supports that side of the debate.  "Processors typically have a ten-year life span," he says, so a PC will be dead weight before switching it on and off could affect the CPU.

Tip: If you're using Windows XP, right-click the desktop, choose New, Shortcut, type shutdown -s -t 00, click Next, give the shortcut a name (for example, Shutdown), and click Finish.  Next time you need to shut down, click the shortcut icon.

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The government reads everyone's e-mail.

Okay, so we thought this myth was spawned by the same conspiracy theorists who gave us the Gunman on the Grassy Knoll, the Illuminati, and Area 51.  After all, how much time does the government really have on its hands?

"It's obviously a myth," says Marc Rotenberg, Georgetown University law professor and executive director of the Electronic Privacy Information Center.  If a privacy watchdog doesn't buy the myth, no one should, right? Wrong.

"The government may not be reading everyone's e-mail now," he adds, "but that doesn't mean it's not interested in doing that in the future.  In a few years, the government might be reading everyone's e-mail."  Fortunately, we Americans have the Fourth Amendment.  Government agencies--the FBI, the CIA, and the NSA--can't read your e-mail without probable cause, except under special circumstances related to espionage.

The Patriot Act allows the government to read all e-mail of a suspect and of all people who communicate with that suspect.  But even privacy watchdogs like Rotenberg don't claim that everyone's e-mail gets the once-over yet.

In the end, conspiracy junkies may feel vindicated.  "There are programs that can sort through mass amounts of e-mail, looking for suspicious keywords," says Ari Schwartz of the CDT.  He says because intelligence agencies haven't been open about whether they are using such software, you can't rule out the possibility that the government is checking up on you.

If you're feeling uneasy, download an encryption utility such as PGP Freeware, and read "Products for the Paranoid."

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Only a pricey surge protector can keep your devices safe.

"I don't see a direct relationship between the cost of a surge protector and the protection it provides," says Joe Wilson, a senior electrical engineer with Eugene Water and Electric Board, the utility company that serves Eugene, Oregon.  "Most surge protectors are based on the same sort of technology, and the response time (how fast they switch on) is similar across the board.

"Often, the more expensive protectors add some simple bells and whistles, such as status lights to indicate that the device is working," says Wilson.  "But that doesn't mean they're going to protect your computer any better."

And don't get caught up in the energy dissipation (most often expressed in joules) and response time features that some surge protectors tout, Wilson advises; they're not a reliable indication of quality.  Instead, just make sure that the surge protector is UL 1449 rated, which means that it meets the Underwriter Laboratory's tested standard.

There's no question that surge protectors are necessary to protect sensitive computer gear from surges or spikes in the power supply.  Although most of us think of outside surges and spikes as the prime suspects, homegrown problems, like those created by appliance motors cycling on and off (think fridge, washer and dryer, and air conditioner), are more common.

Surge-protected power strips won't protect your data during blackouts or brownouts, but an uninterruptible power supply will. UPSs include a battery for maintaining power and enabling you to save data before your PC shuts down.  Newer UPSs have a software component that lets you automate backup and set up shutdown procedures. (For a review of UPSs, see "Power Protection.")  A brownout (flickering lights or a snap-off/snap-on of the power) won't trip a protector, but a lightning strike will.

Warning: The newer the microprocessor, the more susceptible it is to power spikes.  The greater the number of transistors packed into a chip, the less tolerant it is of excess voltage, says Wilson.  If you use an aging computer without a surge protector, it may survive a spike.  A newer PC, on the other hand, will fry.

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If you don't periodically run your laptop batteries down to zero, you'll lose battery life.

This belief stems from a syndrome that plagued old-fashioned laptop batteries--the bulky nickel cadmium variety.  With those batteries, performance degraded if the battery wasn't periodically discharged fully.  (If you use a NiCd-powered laptop, discharge the battery every three months.)

Newer laptops use lithium ion batteries that have no memory, says Isidor Buchmann, the founder of Cadex, a Canadian manufacturer of battery chargers and analyzers.  They don't need to be discharged to maintain their life, he says.  Lithium ion batteries prefer a partial rather than a full discharge.  Nonetheless, every 30 charges or so, you should run them down to zero.  This measure isn't to preserve the battery but to recalibrate the fuel gauge--the indicator on the laptop screen that shows how much battery juice and time remain.

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If you don't use an antistatic wrist strap while tinkering with a PC, you'll ruin hardware.

We've advised using antistatic wrist straps, but some technicians say they're unnecessary.  "I've never worn a strap, our shop's floor is carpeted, and I've never shocked out a machine," says Jake Strouckel, a computer repair tech.  "I've even grabbed hard drives and gotten a shock, but nothing happened to the drive."  Hold cards by their edges, instead of touching the gold-plated circuits, he says, and you'll be fine.

Not that there isn't some danger of frying electronics with static (the proper term is net electric charge).  Though people don't detect a static charge of less than 3000 volts (by the way, it's amps that kill, not volts), sensitive components, such as a CPU, can be laid low with as little as a few hundred volts.

Advice for discharging built-up static ranges from the humorous-but-effective (put a metal sewing thimble over a finger, then touch the thimble to the metal object) to the ludicrous: Wrap aluminum foil over the soles of your shoes.  We tried the foil method, and ended up falling on our you-know-what while trying to walk across carpet.

To be safe, wear a strap, or before you tinker inside a PC, ground yourself by touching the PC's frame with the cord plugged into a grounded outlet or by touching something metal that's grounded, such as a plumbing fixture.