Save avast! 5 download to desktop. Run avast! 5 uninstall tool in safe mode, reboot twice. Boot into safe mode with networking & install avast! 5, reboot. Worked for me & others. I'm very happy to be back with avast! 5 Free on XP sp3, 32bit. I never had a problem with avast! 5 free on 7 64bit.