Upgrading to Windows 8 isn't going to eliminate the Virus unless you format the hard drive and then you wouldn't need the virus software. What do you mean by "Windows 7 boot disk is unavailable for my CPU"? You don't have to upgrade to Windows 8 to fix your PC. Did your PC come with Windows 7? If so, the PC case (tower) should have a sticker containing the Windows Key. Just borrow a Windows 7 disk and re-install Windows 7. You need the same version that is currently installed. Example: Windows 7 Home Premium.