Need to Reinstall Windows

Hello,
I am having all these errors in windows xp pro, after letting my idiot friend borrow my laptop. He probably deleted some important files. One of the errors I am gettting is msiexec.exe application error, also ntrtscarn.exe error, and windows explorer encountered a problem and needed to close. I have all the original disks for my laptop so I was thinking about reinstalling it, but I have a few programs I don't have the disk for and I don't want to lose them. Is there anyway to only reinstall windows and not mess with my programs, or anything else