I'm relatively familiar with some real basic, but real common forms of fake antivirus software. It has been ages since I last dealt with it (I've not worked in IT for a year now), but if I remember correctly, and this may not be any help to you at all. If I remember correctly, if you go to...
It's either
%appdata%
OR
%localappdata%
The thing usually sticks itself into a folder that is approximately 12 characters long, consisting of random letters and numbers. Something like "Ax3vt232egmpd". If you see anything like that, go into it, and see if there's a .exe with the same string, or a different string with the same naming structure.
With that, pop open task manager's process list, and see if anything by that name is running. Kill it, delete the folder. Pop open your registry, run a search for the .exe string, see if anything matches it. You're prooooobably good to nuke that stuff too. But, I am not a computer lawyer, and this may not be the safest thing to do.
This advice may be completely useless to you, but in my experience, I've solved about 30 people's problems with shit like that through those steps. Most of the time they haven't been able to even stop the shit coming up, so there's that.
I will stress that the best way to be sure is to nuke your computer from orbit. Back up important data - the malware / fake anti-virus stuff I've seen isn't smart enough to jump over to usb drives and crap. Then just pop a fresh coat of Windows 7 over your HDD and you should be okay.
As a general suggestion that isn't as drastic, also give Microsoft Security Essentials 2.0 a spin. I find it's pretty good for finding nasty .exes. I use it over spybot and malware bytes (mostly because I dislike multiple security applications, and I'm pretty cautious / aware with my browsing and don't click on stuff / go to sites / let scripts or flash run / etc without my knowledge).
I hope any single thing from this helps you. Advice is not guaranteed to work, don't sue me if your shit breaks, if I'm totally wrong please feel free to yell at my stupid ass for giving bad information.