First off, nMapWin fro insecure.org sucks badly, so don't use it. If you want nMap on windows use eEye's nMapNT, it works correctly.

Secondly, are you just seeking a port scanner? Or a security scanner, vulnerability scanner, etc? If you are seeking these things for windows, you are in luck.

eEye's Retina tool is far and away the best scanner of this type, in fact its CHAM technology has made it the only scanner I know of to have actually _discovered_ new exploits and has bugtraq submissions.

catch