Steven12 he's right. Why have just one? Adaware will pick up what spybot misses and vice versa.
I personally don't like the M$ antispyware program. It's big and clunky and intrudes like Norton.
Also go here for regseeker to clean the registry. As to multiple malware programs, You can run all of them. Only ms antispyware, spywareblaster, and spybot run in the background and I have never seen a conflict with them. http://www.hoverdesk.net/freeware.htm