While most virus scanners will find most notorious trojans, you should also consider adding a trojan scanner to your system.

One you may consider is BOClean, found at http://www.nsclean.com/boclean.html

The other is TDS-3, found at http://tds.diamondcs.com.au/

They're well worth the cost, and TDS-3 also includes some great network tools as well.