MSE is a great free antivirus solution.
See
http://av-comparatives.org/ for a comparison.
I can recommend using 2 on-demand scanners:
- Malwarebytes' Anti-Malware
- SuperAntispyware Free Edition
(Both require manual updates).
Some members use MBAM (Paid) alongside their AV, the paid version has an IP Protection Module, it's realtime protection has also improved.
See
http://www.youtube.com/mrizos for anti-malware prevention videos.
Personally, I'd remove Ad-Aware.
Hope this helps.