The Wiki description of a Trojan is pretty accurate: Trojan horse (computing)
There is the possibility that it could lead to everything (and more) that you describe. The Trojan likely opened a 'back door' into your system from a remote operator somewhere on the internet.
Password changes for your online accounts is a very good idea at this point.
Had you run your AV scan's in safe mode?
Even better, run the AVG Rescue CD
? A bootable CD that can bypass a possible infected operating system (a rootkit) that can often protect itself from AV scans.