I'm using Avast Internet Security (2nd year) and Celframe Free Antivirus (d/loaded Tuesday 7th June), I'm running vista business and it works fine for me. Ran both to scan Avast for C drive and Celframe for D drive, i have tons of directories - files as i'm a web and business developer. I didn't try the facebook or twitter secure login tho cos i do that via my iphone4 but my avast scan took 3hours and celframe took 2hours, avast 6 virus, celframe 8 virus different drives, files equally same +/-. Maybe they fix the bug before i downloaded not sure or doesn't support xp. Who knows, werks for me like gem and keeps my pc clean.