I would suggest buying a new Hard Drive for them that's the same size (old computers like that have really small HDDs so it will either be very cheap or unavailable and you'll have to get a new one) and then buy Norton Ghost or borrow a disk from maybe a nearby computer repair store (I'm sure that they will not mind lending you the disk, if for a small fee) and then boot to the Norton Ghost disk and clone the HDD with bad sectors (set it to master) to the new one (set to slave). I've never tried this so it may not work.

Another method is to buy that new Hard Drive from the same company as the original Drive, and contact that company about data recover services. They should give you instructions on how to send them your drives and they'll get your stuff over without a problem. then just send it back and have yor sister install the new drive. Then have her get some of the fine anti-spyware and antivirus programs on this site make sure the copied-over files aren't infected.