Short of sitting down in front of it, about the only thing I Can advise is system restore, if it actually works...other than that, get the restore CD and reinstall. That’s usually the best way to fix serious problems these days, with anything after XP. Furthermore, with all the seriously malicious software out there, viruses, root kits, spyware, back doors...reinstalling is often the only way to find and fix problems of that nature, they’ve gotten really good at hiding it. And if they can hide it from me, that’s doing pretty good. I’ve built and repaired computers for over 15 years. I found about 6 or 8 years ago they had gotten so good at hiding their malicious software I was stumped...So I just started reinstalling.
If you’re up for an adventure, find and download a Linux Live CD, and try that. I’ve been using Slacko, the latest version of Puppy Linux, it’s pretty good and Linux is a lot more user friendly than earlier versions were around the time I started using it, 2001 or so.
If you don't mind 2 or 3 days of downloading and installing updates afterward. That would be my last resort only after doing research and trying other methods to fix the problem. Everything isn't caused by malware. Sometimes it's just a glitch.
And Linux still isn't quite as user friendly as Windows if you have a problem, since most of the time you have to fire up the terminal and type in the usually unintuitive commands.