DeBank is a simple portable tool that will quickly check your PC for the presence of the 5 most dangerous banking Trojan families: SpyEye, Zeus, CarBerp, Gozi and Patcher.
The program works by scanning the memory of all running processes, looking for chunks of code which belong to each malware variant. This means it's faster than a conventional hard drive scan, and should also be more accurate. (Conventional signature checks can fail if the malware is packed in a different way, but the underlying code remains the same.)
DeBank comes in the form of a Windows console tool, and is very easy to use. Just launch the program - running it as an administrator in Windows Vista or 7 (right-click, select "Run as administrator") - and watch. DeBank will keep you up-to-date on its progress, and either give you an all-clear when it's done, or name the suspect process if it's found something.
Please note, DeBank is a detection tool only: it will alert you to the presence of malware, but won't remove anything. If your system turns out to be infected then you'll need a more powerful package to clean up. Malwarebytes Anti-Malware is a stand-alone detector which should be able to help, or, if you need a full antivirus package, take a look at AVG Anti-Virus Free. And in the meantime, treat this PC as though everything you do on it is being passed to someone else: don't log in to any secure sites or enter any confidential information until you're sure the threat has been removed.