It’s possible to have more than one ASP.NET IIS installed and registrated on one machine (that runs Windows).
To check which version is currently registered run Command Line (Start/Run… and type ‘cmd’) and go to %SystemRoot%Microsoft.NETFrameworkvXXX directory where %SystemRoot% is a special system-wide environment variable found on Microsoft Windows NT and its derivatives (read more on Wikipedia) and vXXX is the directory with ASP.NET IIS files.
Being in that directory, type aspnet_regiis -lv. You will be then given the list of installed/registered versions of ASP.NET IIS.
To register a new version of ASP.NET IIS, go to its direcotry in %SystemRoot%Microsoft.NETFramework (using Command Line) and run the following command: aspnet_regiis -i.
To unregister a new version of ASP.NET IIS, go to its direcotry in %SystemRoot%Microsoft.NETFramework (using Command Line) and run the following command: aspnet_regiis -u.
To learn more about ASP.NET IIS Registration Tool (Aspnet_regiis.exe) visit the description available on MSDN service.
