As far as antivirus goes, AVG is good, but I prefer Avast!. AVG can occasionally slow a system down, but Avast! generally does not. Not in my experience, anyway. It's also free and definitely works.
But as far as registry cleaners go...
Windows Defender and Adaware are my choices for malware protection, but honestly, if I find that a friend/family system has any sort of virus or spyware on it, 99% of the time I feel that nothing but a scorched-earth reinstall can really fix the problem.
I've found that spending an hour or two reinstalling Windows results in a vastly improved system over spending an hour or two trying to hunt down/kill spyware, adware, & virii. Just my opinion. I am a Windows guy, but I still believe that a full reinstall every year or so is a good idea, just to clean out the 'cobwebs'.
Of course
someone ought to chime in that the best antivirus & antispyware is a Mac, or Linux.
