Long story short, I had a friend over on Friday and we watched a movie online at one of those "watch free" websites. He went to a website I wasn't familiar with, but said it was good and safe (turns out he has a Mac so everything is safe for him).
Ended up that the very next day my computer constantly froze and crashed. I had been unable to download anitvirus, execute any scans, OR even download Windows Update. I jumped in and out of Safe Mode, messed around with the registry, and downloaded a lot of antivirus software using my second computer and a flash drive frown emoticon
I tried many different antivirus programs and nothing worked, they only found small things which were warnings and useless crap. I tried Avast, Malwarebites, and TrendMicro. Nothing.
FINALLY I tried BitDefender, and after getting the latest update, I ran a full scan on the computer. It found a Trojan and quarantined it immediately.
Before I restarted my computer, I immediately tried to initiate a Windows Update, and the process began without freezing and crashing! I noticed a dramatic difference immediately after BitDefender removed the threat. Finally back to working condition!
If you suspect your computer was infected with something nasty, not just the typical malware, but something which is making your computer freeze and not allowing you to even run antivirus scans, try everything you can to get BitDefender running on your computer. It is the best one by FAR!