During the pentest, we may sometime need to perform rdp to a Windows server. This can be done using "rdesktop" command. Here is how I do it with my backtrack.
rdesktop -E -z -g 90% [Windows Server IP address]
-E : disable encryption from client to server (to speed up the connection).
-z : enable rdp compression
-g 90% : desktop geometry at 90% of your current monitor.