IMW,
I would suggest that you download and install both SpywareBlaster and SpywareGuard (runs resident).
Both are effective at preventing spyware/malware from getting into your computer. They are freeware.
www.snapfiles.comIf you run Adaware and Spybot once a week, you should be ok, but spyware can invade every time you connect to the net!
Avast and A2 get along just fine.
I usually run ALL "anti" programs once a week including Avast. Update signature or definition databases before running the latest scan.