I'm a personal user of Outlook with anywhere between 4 personal computers
(don't ask why, they all do have a purpose). I'd like to have a shared
calendar that is accessed by each computer where each can view and edit the
calendar.

I don't have Exchange, since it only runs on Server 2003, which I don't want
to pay for. One of my machines is used as a simplistic server (all machines
run XP Pro), however, and would be able to host this calendar, if I could
find a way to do it.