Below are some programs which will detect and remove trojans from your computer.
Anti Trojan 5 (About 4.8mb)
Backwork 2 (About 430kb)
BusJack (About 300kb)
PC Doors Guard - Library consists of 1034 trojans. I'm pretty sure there aren't that many different trojans, so most of those 1034 must be variants of each other, eg server compressed with a different compression algorithm.