I have been asked this question a few times recently, so I figured I would post it for anyone that needs it.
Remote Desktop in Windows 7 is disabled by default. This is good really. Why have any open ports that you are not using? Windows has been bad about this in the past, so maybe this is a step in the right direction. So, how do you enable it you ask?
First, once you are logged into Windows 7, open the start menu (by clicking the start button) and right click on Computer then select Properties.
When the new window comes up, select Remote Settings in the left column. This will bring up the Remote tab under System Properties.
Now you are presented with the options you need to enable Remote Desktop. Select the “(more secure)” option if you are running a newer version of the remote desktop client. If this does not work for you, you may need to either update your client or choose the other “(less secure)” option.
Of course, there is another tool I use alot that I can recommend: http://www.LogMeIn.com
Hope this helps.