This error is not related to Sitefinity. Most probably you have installed IIS after installing the .NET framework. Follow the instructions below as a possible solution:
1. Find the Virtual Directory for your ASP.NET 2.0 application.
2. Right-click for properties and see if you have a tab saying ASP.NET.
3. If you do, see if your 2.0 app is trying to run using the 1.1 version (1.432...)
4. Change that to the correct version of your .NET framework (it should be v2.0.50727).
Also, you can try to repair your ASP.NET installation and set up all of the appropriate ISAPI extension mappings.
For more information on this approach, please have a look at the following blog
Another solution is to reinstall the VS after you install IIS. You can
perform these actions as an alternative.If these suggestions do not help, you can do a search with Google on this error.
Let us know how it goes.
the Telerik team