1st thing to try. Boot into Safe Mode by tapping F8 repeatedly while booting up and then go to Start > All Programs > Accessories > System Tools > System Restore and see if you can take your machine back to before this happening.
An alternative means to start System Restore is to go to Start/Run and type in rstrui.exe and click Enter.
If successful, temporarily disable System Restore to delete the infected restore point.
If not read on....
Boot into 'Safe Mode with Networking' and download the FREE version of THIS tool, update it (important) and then run a full scan ALL IN THAT MODE (it works!).
Hopefully that will get rid of it.
As far as TDSSKiller and ComboFix are concerned, they are best left to the experts on the malware removal forums.