An oldie but goodie. I use this often – http://support.microsoft.com/kb/187623
Regedit.
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp
Change the port number from Decimal 3389 to something else.
You will have to restart the server after this.
PS. To access Remote Desktop quickly, type mstsc -v:[server, IP, or net address] from a command prompt.