Si pones "download.trojan" en el google lo primero que te sale es la pagina de tu antivirus explicando como quitarlo...
removal instructions
The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.
1. Disable System Restore (Windows Me/XP).
2. Update the virus definitions.
3. Restart the computer in Safe mode (Windows 95/98/Me/2000/XP) or VGA mode (Windows NT).
4. Run a full system scan and delete all the files detected as Download.Trojan.
5. Clear Internet Explorer History and files, if needed.
Un Saludo.