Spybot.com it is free. I had to have a new hardrive installed on my computer a few years ago and the computer guy I took it too installed Spybot on my computer for me to clean out the trojans, adware, worms etc. It is free. They offer a spot for donations. I also use Avast for my antivirus.
I just installed it on my mom and sister's computers and found 75+ trojans, adware etc on one computer.
Good luck.