Busting the Biggest PC Myths

Magnets zap your data.

Photograph: Chip Simons
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 CompactFlash 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 CompactFlash 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.

Using a cell phone on a plane interferes with the navigation and communications systems of the aircraft.

"I've never experienced a navigational problem that could be traced to a cell phone," says one veteran pilot who didn't want his identity revealed. "From everything I've read, cell phones and most avionics shouldn't conflict."

So why do flight attendants make you put away your gear before takeoffs and landings? "That's more for making sure [we] have people's attention and for [individual] safety," he says. "If I have to hit the brakes and abort a takeoff, I don't want a laptop flying across the cabin."

The Federal Aviation Administration, which regulates cell phone use in a plane, has a different view: "The concern is that cell phones would conflict with onboard avionics," says Paul Takemoto, the FAA's electronics guru.

Is there scientific proof that cell phones can make planes go haywire? Some. In 2003 the Civil Aviation Authority--the FAA of the United Kingdom--ran tests using simulated cell phone signals in a chamber (not in an actual aircraft) and found problems. In some cases, the compass froze, some instruments displayed errors, and audio communications were difficult to hear due to interference.

Until additional tests prove otherwise, Takemoto says, the FAA prefers to err on the side of caution.

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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