Windows remote desktop is a commonly used protocol throughout many networks. It provides remote access to windows machines when enabled.

Tool
rdesktop

Basic Syntax

rdesktop -u <username> -p <password> <ip address> -g <percentage / resolution></percentage></ip></password></username>

Break Down
-u : Username you wish to log in as
-p : Password you wish to use
<ip address> : Host you wish to connect to
-g : Set’s the resolution you want to interact with the machine over. You can do a percentage of your own desktop (i.e 90%) or a set resolution (i.e. 800×600)

Example

rdesktop -u Administrator -p sup3rs3cr3tp4ass 192.168.1.123 -g 90%
Handy Hint
This registry value when added will enable RDP

reg add "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server" /v fDenyTSConnections /t REG_DWORD /d 0 /f
Advanced Reading
You can do a lot more useful things with RDP such as set the colour depth (a) to help with laggy connections, etc. The above will get you a basic window but there are plenty more options. Refer to the documentation to read more.