Do you know any that will detect and stop "Win 7 Antivirus 2012"?
Find a freeware program called process explorer and figure out which exe is running, restart into safe mode (F8 immediately after bios at boot), and delete the exe. Not a thorough fix, but sometimes does the job.
The problem with these imposter-AV viruses is that many of them modify your registry so that you can't run (exe) programs any longer.