Virtual PC doesn't work the way that I think you think it works. It's designed for one person to use more than one OS at once, not for several people to split a computer.
You could do it relatively cheaply by installing a guest OS that supports Terminal Services / Remote Desktop (e.g. Win XP Pro would do) and using a terminal server client hardware box, but I don't think that's quite what you're looking for either as it is still expensive and difficult enough to make it worth your while just to buy whatever Dell outlet store or whoever has on special at the moment.