My name is Ben Groshek, and I am with STOPzilla online communications.
I can assure you that STOPzilla is definitely not a scam. One thing we should make clearer is that the trial version of STOPzilla does more than just scan and list infections. It actually quarantines the infections, which would explain why the other scanning utilities did not locate any when you ran them. STOPzilla does not list fake results. Any items identified by the scan would be the result of an infection being detected.
Please feel free to contact me directly via the information provided below. I'd be happy to answer any questions you have about STOPzilla, and get you set up with a fully functional version of the program free of charge.
Email: ben at stopzilla dot com
Phone: 1-877-877-9944 ext. 128