Funny scandal ust.avi.exe...virus problem

Question

funny scandal ust.avi.exe....this file comes again n again in my computer after deleting. My computer is geting slower day by day and i m unable to install any new software in it. I hav tried to remove this virus by installing antivirus bt i t didnt work...I hav formatted my c drive and reinstalled windows xp and just after that first installed antivirus,the antivirus program detected the virus n deleted it but my pc have still the same problem. My task manger is also disabled automatically......I dont hav internet connection at home ..i can download the antivirus from sumwher outside only and than can install it so plz tell me any way to remove this problem.....