From MSKB article “How to enable and to configure Remote Desktop for Administration in Windows Server 2003” here:

http://support.microsoft.com/kb/814590

“You do not have to have a Terminal Server Client Access License to use Remote Desktop for Administration. However, only members of the Administrators group can gain access to the server.”

“Enable Remote Desktop for Administration”

“By default, Remote Desktop for Administration is disabled. To enable it, follow these steps:”

“1. Click Start, click Control Panel, and then click System.” “2. Click the Remote tab, click to select the Allow users to connect remotely to your computer check box, and then click OK.”

“Note You do not have to have a Terminal Server Client Access License for Remote Desktop for Administration. A maximum of two concurrent connections are automatically permitted on a terminal server with Remote Desktop for Administration enabled.”