sheesh! Even (or especially) an old Windows machine needs good anti-virus protection. I uninstalled Avast! from Marie because it was getting annoying; that left only Online Armor - basically a good firewall with some anti-malware protection, but not a complete antivirus. Avira would not install (saw something about 'net' flashing by, tried to install recent .NET version but that would also not install!); AVG insisted Online Armor was a conflicting program and wanted it uninstalled (sorry, NO); Panda just would not even download; finally Comodo AV got installed without any grumbles (not even from or about Online Armor), and just finished its first scan: All clear! #phew