I had that problem and it turned out to be a worm virus. the worm i had actually screwed with the circuitry and eventually fried the motherboard, making the computer essentially broken and not worth fixing. If she can get it to run long enough to back up important files on a cd, then run the recovery disks and start from scratch. run a antivirus program, not just a spyware program, to check for viruses. also, do a disk check by going to the c drive properties dialog, tools tab, error check option. this will scan for bad sectors of the hard drive which may be the reason for the defragmenting stopping mid way.