By default when a connection is made via RDP, the bit depth is set to 16. If the user wants to change this, they must change a registry key.
Open up the Registry Editor (Start -> Run -> regedit) and navigate to the following key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp
Change color depth to 4 (leave as hexadecimal)
Reboot Windows XP to have the change take effect.
