You know, I think you shouldn't have left your laptop to your so call friend. He may have be rough with your laptop, and when a laptop is left on and getting shoved around, the hard disk gets damaged sectors. Have you tried doing a thorough scandisk with surface check. I bet you have a whole bunch of bad or damages sectors.
For example if you drop your laptop on the floor while it is ON, you may end up with a whole bunch of problems like the ones you label.
If scandisk shows you have many bad clusters, get a new hard disk before you lose everything and don't lend you laptop; PC means personal computer. Laptop PC is like very personal computer.