We now have patches available for some of the problems folks are having with creating WPF applications and WPF browser applications using the April CTP of VB Express and VC# Express (this is the "beta 1"-era release of Express). You can check out

http://blogs.msdn.com/johnmont/archive/2007/04/26/wpf-patches-for-vb-and-vc-express-ready.aspx for the links to the patches.

Hope this helps.