I think I recall success with this once and do not have in my notes how to do it which means I only did it once. I think I must do it twice to qualify for a copy/paste instruction from me!
If you perform a Google search for:
xp remote desktop multiple
You will get some hits that involve termsrv.dll and a registry adjustment (download a .RAR and follow the easy instructions), but I remember something about using Group Policy and adjusting upward the allowed number of connections which defaults to 1. I did not look at all the Google hits either.
The GP adjustment might be all that is needed nowadays if you are on SP3. That would be Group Policy, Computer Configuration, Administrative Templates, Windows Components, Terminal Services, Limit Number of Connections (enable and increase). My GPE shows it currently not configured, but I know I have messed with it before. If you are using XP Home, we will have to adjust the registry.
I would try adjusting the Group Policy Editor first since it is easy. If you have XP Home, I can tell you how to fix the registry by hand since XP Home does not include GPE.
I can't test it very easily, but this link sounds familiar and I just downloaded the .RAR and looked at it and it is not frightening to me. Just backup the DLL, make a manual Restore Point, if you do the registry fix use ERUNT or something to back up the registry first. ...some common sense!
If I had the means, I would sure give it a shot. Read through the post history - for some folks it works right away, some folks have some cockpit errors along the way...http://alonbilu.wordpress.com/2008/05/17/e...-file-included/
Before making any changes to your registry, back it up with this popular free tool:http://www.larshederer.homepage.t-online.de/erunt/