Trojans are software programs devised by professional hackers to detect activity on a PC allowing the hacker to assume the user's identity.

A lot of anti-virus scanners don't really check for Trojans, although more & more of them are starting to do so. To be on the safe side you should use a Trojan scanner that can be updated just like your virus scanner.

A free online Trojan scanner to check for Trojans

Some free Trojan scanners

Swatit Trojan Scanner

a-squared a² is a complementary product to antivirus software. It provides specialist protection against harmful software. Antivirus software is not enough! a² provides protection against Trojans, Dialers and Spyware. a² fills the gaps that malware writers exploit.

"The Cleaner" is free for 30 days and removes most Trojans.

"Tauscan" is free for 30 days and removes most Trojans.

A great site for Trojan information is Hackfix, the site that's dedicated to helping people stay informed about Trojan horse programs, how to find out if you are infected, and how to remove these Trojans safely from your system.

There are several Trojan scanners you can buy. One is PestPatrol.

Pest Patrol can remove a nasty called IQuickSearch.

Another Trojan scanner is TrojanHunter.  TrojanHunter has a free trial.

Trojan Remover   From Simply Super Software. Free trial as well

Mike's Program Update List

Important!

If you have a virus or a Trojan on your Windows ME or Windows XP computer, you will need to turn off System Restore once you have cleaned the offender from your computer.

To turn off System Restore:

Open System Properties. To open System Properties, click Start, click Control Panel, and then double-click System. In the System Properties dialog box, click the System Restore tab.
Ensure that the Turn off System Restore check box is selected. 
 
After System Restore has been turned off and your computer no longer has a virus or Trojan, then turn System Restore on again.

To turn on System Restore:

Open System Properties. To open System Properties, click Start, click Control Panel, and then double-click System. In the System Properties dialog box, click the System Restore tab.
Ensure that the Turn off System Restore check box is cleared.