If you are getting error messages with ASP.NET and you installed IIS after installing VS (instead of the other way around) you need to register ASP.NET manually. 

Here's the easiest way I know how to do this if you install VS and IIS in that order:

  • Open the Visual Studio 2005 Command Prompt using the shortcut on the start menu.
  • At the prompt, type: aspnet_regiis -i -enable

9 times out of 10 this seems to help unblock anyone who is trying to learn ASP.NET 2.0 for the first time on a Whidbey install and didn't have IIS installed first.  I can't claim this solves every ASP.NET problem in the world, and there are probably environments when this is not the right advice, disclaimer, disclaimer, disclaimer...