Hello,
Are you referring to the viewer program, or the server program?
The server program is called Terminal Services, and it can be found on NT Server, 2000 Server, 2003 Server, and XP Professional. Not sure if it is on XP Home or not. When run in administrative mode, it can support up to 2 connections from viewers.
The viewer program may be found a variety of places. For Windows XP/2000, go to Microsoft's website, and search for Remote Desktop, and you should find it. If you have a Mac or Linux box, you can find free viewers out there on the internet, too. Beware that the Linux version requires Xwindows, and a command line command to fire off the remote session.
I use RDC and the various viewers on Mac and Linux all the time to keep the Windoze farm in line.
Christian