trojan scanners on my security site:
http://multifinanceit.com/it/security/security.htm
Look at the links under
Security.
I regularily run these tools.
There are more Online scanners in the "Links" collection.
CTRL + F + OnlineVirusScan
And I reccomend:
http://www.abtrusion.com/
or this free tool:
StartUp Guard v1.0:
http://www.acelogix.com/download.html
They prevent access to the registers without your permission. And do not forget Pctools Spyware Doctor with onguard protection.