A similar thing happened to me on Win XP system, only all of the drives
in My Computer disappeared. Nothing but a blank white page when I opened
My Computer. I could however use the drop down location list in My
Computer to select a drive, and then files and folders on a drive would
show normally.
I still don't know what caused it, except that close to the time it
happened I was playing with a settings tweaker program that had the
ability to hide drives. I didn't use it to hide the drives, but they
nonetheless disappeared, and that program couldn't restore them.
I was that way for months, until I finally found out about XP Pro's
Group Policy Editor. It's not in Win XP Home, but you can download it
from the following link. With it I was able to un-hide my drives finally
and all is will.
http://files.filefront.com/GPEdit+Fileszip/;6235551;/fileinfo.html
Later, Ray Parrish