file associations

Yesterday, for some reason all my file associations in my registry were wiped off. I cannot open .exe files anymore and restoring the value "%1" %* as it should be for the .exe file doesnt help. I've tryed safe mode, booting linux on a cd, nothing helped. Anyone has another idea on how to fix this?

btw I'm using Windows 2000 pro and nothing else has been lost on the pc: my files are still there but the file associations are all off.

There is a repair option for windows 2000 but no repair install like with windows xp. I managed to restore the file associations with a backup from another pc running with windows 2000 and now at least the computer is working. The problem now is that it is a little bit unstable: "Add/Remove programs" in Control Panel doesnt work, some programs dont work either.

My dad suggests updating to windows XP, but I wonder if I would lose anything on my current system?