Problum of funny virus

Question

HI
This is sunita. I am a student of cse B.E. IInd in M.B.M. engg. college. I have a funny virus in my PC. I don't want to formate my PC.Alrady twice I formated my pc. I can't work at my pc. I want to install a updated antivirus but due to funny virus I can't do. How I can uninstall my old antivirus and install updated antivirus without format pc. Plz replay me as soon as.