Before you resort to a reinstall, there are several other things that you can try.
First, have you tried using System Restore to roll your computer back to a point before the problems started? You won't lose any data, but you might get rid of the original problem - just make sure that you choose a restore point before the date/time when the problem first cropped up.
If you have trouble running System Restore in normal mode, restart your computer in Safe Mode and run it from there.
I suggest you watch this video before you use System Restore.