Visual WebGui application should also be able to run on IIS5 on your XP box, but having a multiuser web application running on an XP box is probably not a good idea, because of the limited connections that XP has for active connections. Don't remember exactly how many, but I think they are max 10.
You should be able to find information for IIS6 settings at the bottom of this article here, and for your XP it would be very similar.
Please let us know if you need any more assistance on this subject.
Thanks Ewan for your help here,