I installed Visual Studio 2008 Professional this morning. That installation went without a hitch. Just now I installed the Silverlight 1.1 Tools Alpha for Visual Studio 2008, which Scott Guthrie let us know about a couple weeks ago.
To test, I created a new Silverlight C# project in VS 2008, and built it. Immediate problem:
The type or namespace name 'Windows' does not exist in the namespace 'System'.
Thanks to Google, I found a forum post from samsp that pointed out the problem: I didn’t have the Silverlight 1.1 Alpha Runtime (September Refresh) installed. This required an uninstall of the Silverlight 1.0 runtime, which was easy.