I found this on another web site and will give all credit to the people on www.thelazyadmin.com;
You've left the site, to finish a job remotely from the comfort of your house, office, bar or car except you've forgotten to enable remote desktop on the server!
As long as you have access to the network and a pc or server on the network your good to go.
Log onto the pc or server and follow the instructions.
Run REGEDIT on your XP workstation or on your Windows 2000/2003 Server. Click on File, then choose "Connect Network Registry". In the Select Computer search box either browse Active Directory to locate the remote server, or type its name in the dialog box.
In the remote machine's registry browse to the following key: HKLM\SYSTEM\CurrentControlSet\Control\Terminal Server
Under the Terminal Server key find the value named fDenyTSConnection (REG_DWORD). Change the value data from 1 (Remote Desktop disabled) to 0 (Remote Desktop enabled).
Reboot the remote machine for the change to take effect.
You can easily do so by opening a command prompt and typing the following command: shutdown -m \\srv1 -r
After the remote machine reboots, Remote Desktop will be enabled on it. To test this from your workstation, open Start -> All Programs -> Accessories -> Communications -> Remote Desktop Connection. You can also type mstsc in the Run command.
Enter the name of the remote server in the Remote Desktop Connection logon box, supply your administrator password when prompted, and press Enter or click Ok.
Magic. Now if you have a firewall in place, you can redirect a few ports to different pc's and servers on the network and use those to gain access. A good port range to use is 22XXX