As far as XP is concerned, I don't know much about its security, but I can tell you this: some of the hacks displayed as being for NT do apparently work for Win2k. I am not sure about how it goes for XP, but my best guess - not that you were asking for a guess - is that some exploits for NT/2k could possibly apply for XP also. One good way to keep up with this is to go to Security Focus website here and sign up for the bugtraq mailing list for "NT." This will help you keep abreast of security of the M$ OSs. I hope this helps.