Hi there, first off I dunno if you've tried malware bytes or adaware:
http://www.lavasoft.com/products/ad_aware_free.php
http://www.malwarebytes.org/
Both have a decent track record for finding the more potent viruses.
Alternatively, if you feel like a challenge, take a look if there's any suspicious looking processes running in your task manager. By suspicious i mean anything that has a gibberish name like awts97rs92, or anything doesnt look like something u'd expect to see on your computer (foreign looking programs etc...). If you do find any, double check them by doing a quick google search to see what they are. If by chance you should happen to find something that is both suspicious and doesnt come up on google search (or better yet comes up as known virus on google search), then chances are you u've found your culprit. If you right click on it you can view the file location the process is running from.
Now when it comes to deleting these files, there's two things to bear in mind. First off there is likely a second folder hiding somewhere else that will re-copy the files if you delete them. These secondary folders often also have suspicious names and like to hide in places like appdata (you can access apdata by typing %appdata% into the start menu's search bar). Other favourite spots are system32 and the temp folder. You want to delete these hidden backups as well as teh virus.
Another possibility is that when you try to delete it, windows prompts you with an error, saying that the files are essential system files and cannot be deleted. In this case it means the virus has tagged its files with the windows system attribute. The easiest solution i found to this (albeit I suspect not viable option in your case) was to start the computer up in a non-windows OS, like Ubuntu, and delete the files from there, as any non windows operating system will ignore the system attribute I mentioned.
Failing that, or if that all seems too erm.... lame... to do xD, then I agree with the other poster, reformat and reinstall windows. The virus will not survive that.
EITHER WAY, that's my 2 cents, lol, hope you have some luck with whichever way you choose to approach the situation. Though i'd deffo try those two antivirus programs if you can first.
GOOD LUCK!