Malwarebytes' Anti Malware
Spybot search and destroy
Hijack this

If none of the above report anything, your operating system is no longer under your control and it needs to be wiped. You're probably part of a botnet as well.

If you can find the actual file, scan it to see what it is:
http://virusscan.jotti.org/
http://www.virustotal.com/