What happens if you install you Visual Studio then realize that you need IIS for you application to test and run. We often do this. I have seen people uninstalling Visual Studio and then installing it again after IIS to make sure ASP.NET works fine.
Wow!! There is an easy way to do it,
Open the command prompt for Visual Studio 2008. Run the following command
Install this version of ASP.NET and update scriptmaps at the IIS metabase root and for all scriptmaps below the root. Existing scriptmaps of lower version are upgraded to
this version. (this is from product documentation help text)
You can also check if the specific ASP.Net version is already attached with IIS by using –lv.