Kevin,
To the best of my awareness, there is no version of .NET where you can run web apps/XML web services using XP Home.
The reason is that you can't run IIS (or even Personal Web Server) on XP Home. So I believe this is more an operating system restriction than a .NET version restriction.
One of my laptops last year came with XP Home. I found some web sites that show some ways you can hack the registry, but after reading them (and one or two horror stories by people who wish they hadn't tried it), I bit the bullet and upgraded to XP Pro. So if you plan on doing any serious web prototyping on your computer, you should find out if there are any hardware restrictions for your box running XP Pro (I've read that a few hardware models here and there might have some driver issues going from Home to Pro, so you should probably investigate that).
Kevin