ASP.NET 4.0 Applications can not run on IIS 5.1

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Some people are still using Windows XP Pro which only installed IIS 5.1. When you try to run ASP.NET 4.0 web application, you might meet the following error message:

Server Error in '/TestWeb' Application.

Configuration Error Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately.

Parser Error Message: Unrecognized attribute 'targetFramework'. Note that attribute names are case-sensitive.

Source Error:

Line 14: Line 15: <system.web> Line 16: <compilation debug="true" targetFramework="4.0" /> Line 17: Line 18: <authentication mode="Forms">

The resolution:

Run the following command:

aspnet_regiis.exe -i

The location where aspnet_regiis.exe resides:

c:\windows\microsoft.net\framework\v4.030319