Hmm...if it is indeed a trojan, I would attack it with an array of antivirus/antimalware tools. AVG, Ad-Aware, Spybot, Avast, etc. are all good, and you should at least get the first three, regardless if you want to remove the virus manually or reinstall Windows 7 altogether. Don't forget to update and run them on a regular basis.

Also, in case you didn't know this, be especially wary of .exe files. From what I understand, hackers just loooooove to piggyback on these files. Download them from a trusted source. In fact, that generally goes for all files. Get them from trusted sources as much as humanly possible.