Had a paid version of a symantec product on my laptop and it kept throwing up alerts about a trojan.gen but failed to get rid of the source file. I tried Ad-aware as a secondary level protection and ran a full scan. Hurray! It found the malicious file that was right under my nose all the while and cleaned it up. Now the alert messages from symantec have stopped.
However, the quick scan failed to pick up the threat.
A free software doing better than some paid ones; that's ad-aware for you.