bit the bullet and downloaded the Visual Studio 2005 CD images from Microsoft, and installed the latest runtime on my Web server.
Only one site broke: Hired Wrist, my dad's site, which I just now fixed. That's not bad. Usually upgrading hoses everything.
Hired Wrist broke (gracefully, I should point out; only the graphic headers were affected) because the released version of ASP.NET 2.0 handles page names slightly differently, which caused my resource-based graphics handling to fail. Resources, apparently, are now case-sensitive. Oops.