Sure, the only issue involved with multiple virus scanners is if both are doing on-access scanning (files scanned as they are used). On OS/2 Norman is the only one that I know of that could do that. Even on windows you can have more than one Antivirus installed so long as both are not attempting to do on-access scanning (you don't really want both running scans at the same time as it would well and truly cause disk thrashing).