Remote desktop - With other user still logged on?
Solution 1:
If you log in as the same user as the already logged-in user, then you will take over their session. However, the user sitting in front of the PC will be disconnected from the session and see the login screen. If the user logs in again, then you will be disconnected and the user continued from where you left off. At no point is the user's session terminated - the programs continue running.
You can use Windows Remote Assistance, which is based on the same technology as remote desktop. It allows you to view and optionally control the current user's session without them logging off.
Another alternative is Remote Administrator, which I used heavily before remote desktop became widely available.
Solution 2:
If I understand your Question correctly , No. Windows XP can only have **1 SESSION ** active at a time. you will need to be running windows server if you want to have more than one ACTIVE session.
Solution 3:
When you want to have an interactive session you use Remote Assistance instead of Remote Desktop. The features as well as the overhead used by a computer to keep most of the third party remote desktop/assistance sessions waste facility, waste bandwidth when they constantly collect information about who is connected even when not being used. They are also a point of security issue when they constantly run.
The out of the box Remote Desktop and Remote Assistance within XP and 7 are more than adequate to control and share all the facility from the connecting machine to the recipeint machine.