In use? Sounds like the virus boots as soon as Windows loads.
I could recommend that you pull up task manager and end its process, but if you don't know what your doing your computer will not like it and force you too restart.
So what I'm going to recommend you to do is boot into safe mode by pressing 'F8' before the Windows Vista loading screen. Doing so will pull up a list of options of where to boot too. Select Boot to Safe Mode and try running a virus scan there.
Safe mode is designed to only launch core system processes so the virus will not be launched (hopefully)
Do a scan and try and fix the virus like nothing is wrong.