I know it would be simple for a lot of people reading this blog :). But the easiest way to remote desktop into a windows machine using a X based linux distro is to install rdesktop.

http://www.rdesktop.org

For ubuntu and debian based distro, fire up the console and type

sudo apt-get install rdesktop

This would install the client.

rdesktop <server IP/domain>

This would fire up the windows remote desktop stuff.