I have spybot S&D
I have MalwareBytes
I have Clamwin (No realtime scanner) older version with current updates.
I have sysgate personal firewall which Avast interferes with.
I have Avast 7 (Which I am not sure I want to keep & from some reason Avast forum posters don't like spybot s&d and said to get rid of it, I am keeping it).

The reason I am considering getting rid of Avast, I have a low memory system with windows xp sp3. I am really not sure about the cloud technology especially on dial-up (Yes, I am still on dial-up). From my understanding it stores your files on remote server. I scan all files I download with the exception of what plays in the browse. Realtime scanners seem to eat to much memory.

LavaSoft Ad-aware runs to slow on my system. I don't have that installed.