On my Win7 home computer I'm running AVG to keep virus/trojan free and once in awhile I'll scan the PC with Malwarebytes. 100% bug-free for years.
We use Malwarebytes at work to cleanup all the spyware/malware, it works great, make sure you update it before you run a scan. If Malwarebytes is removing something bad and it comes right back you should boot the computer into safe-mode and run a scan. If that doesn't remove the little buggers then the best solution might be to backup your data, wipe out the harddrive and reinstall the OS of your choice.