If you are talking about Remote Desktop Connection,
1) On the host, Right-click My Comptuer--> Properties-->Remote Tab-->Check the box "Allow users to connect remotely to the computer"
2) On the host, Start->Run->type "firewall.cpl" with no quotes, hit <enter>-->Make sure "Remote Desktop" is checked under the Exceptions tab
3) On the host, Start->Run->paste the following line in and hit <enter>: cmd /c ipconfig&pause
4) Make a note of your IP address!
5) On the client, Start->Run->type "mstsc" with no quotes, hit <enter>
6) Enter the IP address from #4 next to "Computer" and connect. Then enter user and password. Note: the user MUST have a password ... if no password it will fail.
7) If you are put this on the Internet, you'll have to forward the port from the router. (See http://www.portforward.com
) I'd consider changing the remote desktop connection listening port as well, and if you do that, don't forget to add a port exception in the firewall.