I had Avast, but when it updated to 5.0, I couldn't update. I've uninstalled Avast and tried to reinstall, but no luck. It tells me something about not being able to start because the side-by-side configuration is incorrect. I get the same thing when I try to download AVG or any other antivirus.
Today my girlfriend attempted to download iTunes, but not even that would download.
One suggestion I've found is to download C++. I've tried that, and when I do, it tells me something about error 1935.
This has all been going on since my laptop was unplugged and died during a Windows update.
I've tried a ton of stuff, and I can't really recall what I've attempted so far. But, nothing has worked.