A free tool is also here available, this is from an AntiVirus prog I am running since some time, does self-upgrades (sometimes twice a week!!!) and installs as a virus checker on all major chat systems (MSN, ICQ, YAHOO.....) as well as ir sets up a system internal proxy on the PC which feeds all mail through it before it reaches the mail client...
A total of 134 mails received in the last 4 days have been "isolated" and subsequently deleted by me as infected. Needless to say that there was mail from trustworthy senders...
Here is the link
http://www.bitdefender.com/html/free_tools.php 