Cant install any anti virus or antispyware

Hello,

ive already formatted my pc but stil i cant install any antivirus or anti spyware, i tried to delete the partition and heavy format but still when im trying to install an antivirus, the message will always be "the file is corrupt" or any other message. ive tried all sites to download an antivirus thinking maybe the file i downloaded is really corrupt or something but the message is the same. before i format my pc whats happening was the virus was making a folder with the same folder name. and another thing, i cant format the disk using its own what i did was i took the disk and format it using another pc, then i was able to format it using my own pc.. i only installed windows xp sp2 to prevent getting another virus, but still i have the same problem.. please help.. i asked my friends but all they are saying is that virus is impossible to be encrypted in disk, it should be clean once i format it.. but whats happening to my pc????