I have had a trojan horse also. The only way I was able to get rid of it was through a program called solo anti-virus. You can download a 30 day free trial. Ad-Aware did not work for me, but Solo worked great. Here is the link.
http://www.srnmicro.com/ Just click on downloads.
Good luck.
On edit: As someone else mentioned A system restore is a great option also.