The DSNS network scanner is worth looking into.
It is an advanced network scanner for Windows 2000/XP. Very handy to identify network devices, and to discover what services they provide (such as HTTP).
DSNS Network Scanner is an advanced network scanner for Windows 2000/XP that lets the user perform fast syn scanning to find open ports. This scanner also allows the user to probe any services that may be running on open ports.
Of course, this software can be abused in the wrong hands, so it is often listed as a threat on security websites.