Ms av virus has infected my pc. can't seem to do anything. need help please??!!?

i have been infected with a virus that seems to have taken control of the majority of my computer functions. my hard drive, c: , doesn't show any longer and i have no authorisation to access task manager to end the applications. in safe mode(administrator) the hard drive does show and i thought i deleted everything from that but when i restarted the computer normally nothing has changed. i will beat my computer severely unless i can get this resolved. PLEASE PLEASE HELP????