virus/malware not showing up on scans

New to this but anyway, I have successfully removed stuff and junk from the old box but this one has me stumped. I have scanned with Malwarebytes, Spybot, Adware and Avast and nothing is recognizing that I have something going on. Hit a site yesterday that wanted to "scan" my computer. Avast caught it right way but when I hit "Abort Connection" it started to do it's little trick anyway, defeating my Avast and disabling the resident Scanner. Before writing down any info (like a rookie) I panicked and Xed out of Firefox. This morning when I went to take it out of Stand By it was froze. So I reluctantly rebooted and went strait to the Scanners above. All four of them said "No Prob" "0" infected files.

Still can execute in Safe Mode but the system completely freezes up after about 2 min of use in normal mode causing me to reboot. So what the hell do I do now. Hopefully you say, "Back up all your stuff and Buy another computer "

I run my own business and don't have a lot of time to mess with this and if it's going to cost $100+ to send it in, then I may as well just spend the few extra $100 to get a new tower. I know that is a little dramatic but as you can see I'm a little worried.

"Give me, give me. I need, I need" Bill Murray, What about Bob

Thanks

Bob

It ended up being my registry. I downloaded "Free Windows Registry Repair" and it did the trick. I also went to Window Safety Check and did a scan