What is a Trojan?
A Trojan is spy ware that performs unexpected or unauthorized, often malicious, actions. The main difference between a Trojan and a virus is the inability to replicate. Trojans cause damage, unexpected system behavior, and compromise the security of systems, but do not replicate. If it replicates, then it should be classified as a virus.

A Trojan, coined from Greek mythology's Trojan horse, typically comes in good packaging but has some hidden malicious intent within its code. When a Trojan is executed users will likely experience unwanted system problems in operation, and sometimes loss of valuable data.

How do I remove a Trojan?
In most Windows you'll do the following, each version is a little different:
In Windows XP: Go to My Computer > Control Panel > System > Performance > File System > Troubleshooting; then click 'Disable Restore System'. Then restart computer from scratch (as directed).

In All Windows: Go to add/remove programs in your control panel and uninstall BRIDGE and P2P (If they are there).

Run Spybot Search & Destroy which can be found at Marshall County B.O.Ed. support website. Make sure it is updated or it won't catch everything. Fix all items it finds that are in red. Spybot S&D > Immunize > Recommended miscellaneous protections.

Run latest AVG version 7.x software. Make sure it is updated or it won't catch everything. This will now be able to pick out the Trojan virus & heal it.

Now in XP turn back on 'System Restore', if your system had this option. Restart computer.
ONE WORD OF WARNING! By disabling the 'system restore' it loses its previous restore dates. It begins from the time that you restarted the computer.

On restart run both programs again.

Then go to START>>ALL PROGRAMS>>ACCESSORIES>>SYSTEM TOOLS>>DISK CLEAN UP and clean everything on the list.

If you believe your AVG has been infected, then get an online virus scan here: http://housecall.trendmicro.com/
Trend Micro PC HouseCalls (Click AutoClean before Scan)
BitDefender ScanOnline (Scans for Viruses and Spyware, takes twice as long as others)

Symantec list of Download and Downloader Trojans
http://securityresponse.symantec.com/avcenter/venc/auto/index/indexD.html