Paul,
Sorry for the confusion. I guess I didn't realize you were taking computers home. Do you not have computers at home, which can log into the computers at work?
However, if you are really dead set on logging into the "Main Computer" at work, you will need to use terminal services. Not only that, you will need to do some configuring to allow more than one connection. I believe it will allow three. Please see the following article. If you follow it verbatim, you should have no problem. That is, if you know how to set up Remote Desktop, which is fairly straightforward. If you need help let me know.
http://riccardo.raneri.it/blog/eng/index.php/2006/04/24/windows-xp-multiuser-remote-desktop/
