Hi,
Sorry to hear about your problem. Please follow the directions NateR the Symantec Employee gave you on how to send the upload and send the file. By the way, Malwarebytes' Anti-Malware is free, what you saw is a little ad on their homepage pointing out that if you want better protection you have to pay. However, in this case, use the free version.
Also, upload the suspected file to virustotal.com to see how many AV scan engines detect it as a threat and are willing to remove it, or if it's a false possitive.
Some good free AV's and Anti-Spywares/firewalls that might be able to help you are: Malwarebytes' Anti-Malware, SpyBot- Search and Destroy, SuperAntiSpyware, ClamWin/ClamAV, Spyware Terminator, Kaspersky Free Online Scan, Panda Free Online Scan, avast!, AVG Free Edition.
I can provide links to any of these if you need them. Good luck!