Before we get all techie and very specific here, remember: we have almost no information (other than the OS) about what is really happening here -
1. How big is the hard drive?
2. Is it a hard drive or SSD?
3. What is the computer being used for? Net cruising? SETI calcs?
4. What is the liklihood that the disk is actually full of valid files?
5. Does it only happen on one app or everything? Which app(s)?
6. How much RAM?
7. etc.
I don't go to the doctor and say, "One of my legs hurts." and expect him to say, "Here. Take this pill. Next."