QDo you know of any software that will recover as much data as possible from a severely scratched CD-ROM? I am trying to copy a 50MB file off a CD-ROM that has a large scratch. Windows gets halfway through and then says that it can't read from the device.

A CDs, whether they are audio CDs or CD-ROMs, are easily damaged. CD-ROMs are particularly sensitive to even small scratches. The information on a CD is stored on a thin reflective aluminium layer covered by a clear protective coating. Because CDs work by reflecting a laser beam off the aluminium layer, scratches in the coating can interfere with the laser beam. This causes audio CDs to skip and CD-ROMs to generate read error messages. Unless the scratches are deep enough to reach the aluminium layer, your files will still be there. All you need to do is fix the coating.

People who burn their own CDs should note that one of the main differences between cheap and more expensive blank CDs is the thickness of the protective coating. Cheap CDs are more likely to be irrevocably damaged by a scratch.

If you have problems with a CD, the first thing to do is give the disk a thorough cleaning in case it is dirt and not a scratch causing the problem. This involves wiping the disk with a non-abrasive cloth. When wiping a CD you should always wipe from the centre out, and not in a circular motion.

You can buy scratch repair kits from places such as Dick Smith Electronics, Tandy and music stores. These include a special abrasive liquid. A cheaper solution is to use a metal polish (eg Brasso), a plain white toothpaste or a plastic cleaner. However, if the liquid is too abrasive you may put more scratches on your CD than you remove, so you might want to test the liquid on a CD you wonÆt be too upset about if it is damaged (your kids' Spice Girls album springs to mind). You will also need a soft, non-abrasive cloth. Pour a little bit of the liquid on to the cloth and rub over the scratch, remembering always to rub from the centre outwards. You donÆt need to remove the scratch altogether. You only need to smooth it out so that the laser beam will successfully pass through.