Alright mate, calm down. Try installing the newer .NET Framework 3. Runtime errors are often associated with .NET Framework.
And of course here's the complentary links.
Windows XP 32 bit/Vista 32 bit
Windows XP 64 bit/Vista 64 bit
Hopefully this will work for you - if not come straight back again. Sorry for making you reinstall, I understand how much of a pain it is - but simple solutions first.