Steve Alexander: Data recovery determined by what's wrong

Q We have an iMac G3 that froze. I restarted it, but it will not reboot completely, even though I tried the separate start-up disk. While the hard drive runs, it appears that the data on the drive have been corrupted by something. I have a lot of genealogy data on the disk that I'd like to recover. Any suggestions?

MEL MCPhail, Plymouth

A The question is whether your hard drive is repairable (that is, data stored on the disk are corrupted but the drive itself is working) or whether the mechanical parts of the drive are failing (which means it's time to copy as much of your data as possible onto a new drive before your existing drive quits completely).

If the problem is data corruption, Apple lists several programs that may help you find and repair the damage. See www.startribune.com/a4002.

Alternatively, you can take your computer to a repair shop (I found several by Googling "Minneapolis disk drive repair"), which can either fix the data corruption or copy your data onto a new drive (you'll need to take along your operating system disk).

If you must have your hard drive's contents transferred to a new drive, be sure to say that you want everything copied. When my PC's motherboard failed, I had my hard drive copied to an external drive. Later, I discovered that the technicians had neglected to copy the My Documents folder. As a result, much of my iTunes music was lost by people who should have known better.

Q Please explain the differences between a DVD-RW disk and a DVD+RW disk. Sales people give me vague or different answers.

A They represent different formats for storing data on a rewritable DVD disc. DVD-RW and DVD+RW are two of the most widely used of these formats; they differ from older formats called DVD-R and DVD+R that only allowed data to be recorded once.

You only need to worry about these formats if your DVD recorder is about four years old; machines of that vintage typically required a blank disc with a particular format. Most of today's DVD burners can handle several different recording formats. Check your owner's manual to learn which disc type you need. If you are playing prerecorded discs in a standard DVD player, it doesn't matter whether they are DVD-RW or DVD+RW, because your machine will play either.

The new high-definition DVD players probably will lead to a new alphabet soup of file formats, so get ready to relearn all of this stuff in a couple of years.