Generally speaking, you can use remote desktop from anywhere you please, from over your LAN (local area network) or even from over the internet. Configuring a standard Windows XP box to receive remote desktop connections is very easy.
By the default, any Windows XP machine will only allow one remote connection at the time. In order to enable remote desktop support to a XP machine you will need to do the following:
1) Right click on my computer, go to properties under the "remote tab" select the second option remote desktop "Allow users to connect remotely to this computer"
2) If you have more than one user account set up in your XP machine, you will need to click on the "Select Remote Users" button a dialog box will pop up, in there you will need to enter a designated user account, unless you use an Administrator account which by default is already a member of the "Remote Desktop Users" group.
3) By default Windows Remote Desktop operates on port 3389, you will also need to ensure this port is enabled/allowed in the Windows Firewall exception list, or otherwise any incoming remote desktop connection destined to this machine will be denied.
4) To access this machine remotely from within your LAN, you can go to Start->Run and then type MSTSC at the dialog box and press enter. You should receive a small remote desktop dialog box prompting you to enter the IP address or the hostname of the remote computer you are trying to access.
5) You should by now be presented with a logon screen of your remote computer, be advised that by design if your administrator account or any user account does not have a password set, it won't allow you remotely login, until you have created a password.
6) Now accessing your computer remotely from over the internet, is the same as you would do on your local LAN. But in order to successfully log into your computer, from over the internet, you will need to log into your modem/router and set up a forward port 3389 and specify the IP address of the computer you are trying to access. If you forget to do this step, you won't be able to access the computer from over the internet.
7) Now for security reasons, Windows Remote Desktop is not considered a very secure option, that's why users in other forums or on some internet websites recommends you to use a third party software like TeamViewer.
Hope this helps, let me know if you need any assistance.