Sorry if this seems a little "know it all"-ish, but generally, a backup should not be kept on the same disk that you copied it from. If the disk failed, then you'd lose all the backup, too.
Best to copy all the "essential" stuff (personal files, address books, etc) to a CD or DVD, or think about using one of these Internet backup facilities (Broadband would be better for this). After copying them off the computer itself, test it by copying it back on or testing ZIP files, etc, to make sure the backup works, and then delete the backup off the harddisk.
That is unless I misread the post and have just made myself look a prat........... Very possible.