It may be your best bet to reformat your PC by reinstalling the OEM disk (HP manufacturer disk with Vista, drivers, ect) and then
upgrade to Windows 7.
http://www.microsoft.com/windows/windows-7/
Microsoft has pretty much admitted that Vista is bunk (remember Windows ME?) Personally I wouldn't even bother to fix any unusual problems on Vista without starting fresh. Don't waste your time screwing around!
I'll admit I'm a bit of a "formatoholic" but it has always worked well for me and has solved ALL of my and other people's problems I have encountered.