Win2k Pro has IIS 5.0 and it is not just a personal version. It will fully run a website. I use it all the time and can hold as many connections as my bandwidth will allow. If you like, I can start IIS on my Win2k Pro machine and people can hit it to test.
For getting around a dynamic IP address, you can use a dynamic DNS host like www.dyndns.org and download one of the listed IP update clients. I can recommend one that works great with even using NAT.
If yahoo! was a little above your head, then I imagine running IIS and dynamic DNS will be too. No offense intended, and I'll be glad to help advise you if you need it. Really, your best bet is getting a good paid hosting service or Brinkster.