How to unblock installation of the .NET Framework 4 beta 1 on Windows XP Media Center and Tablet PC Editions

Question:

I tried to install the .NET Framework 4 beta 1 and Visual Studio 2010 beta 1 on my Windows XP Media Center system.  It fails to install with an error like the following:

Microsoft .NET Framework 4 Beta 1 cannot be installed because an incompatible version of .NET Framework (v1.0) is installed on the machine. For more information, see http://go.microsoft.com/fwlink/?LinkId=91126.

I don’t see any useful information in that link, and I don’t see an option to uninstall the .NET Framework 1.0 in the Add/Remove Programs control panel on my system, so I’m stuck.

Is there any way I can install the .NET Framework 4 beta 1 and VS 2010 beta 1 on my Windows XP Media Center system?

Answer:

Officially, the .NET Framework 4 beta 1 (and therefore VS 2010 beta 1) is not supported on Windows XP Media Center Edition or Windows XP Tablet PC Edition.  However, the wording in the readme is a bit vague.  Item 2.1.1.1 in the .NET Framework 4 beta 1 readme says the following:

Note: You cannot install the .NET Framework 4 Beta 1 on operating systems that have the .NET Framework 1.0 built in.

As I previously wrote in this blog post, the .NET Framework 1.0 is installed as an OS component on Windows XP Media Center Edition and Windows XP Tablet PC Edition, and it cannot be uninstalled on those versions of Windows XP.

If you are running Windows XP Media Center Edition or Windows XP Tablet PC Edition and want to be able to install the .NET Framework 4 beta 1 and VS 2010 beta 1, you can manually rename the following registry value:

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\policy\v1.0]

If you do this, there are a few important caveats to keep in mind:

  • Renaming this registry key will cause the .NET Framework 1.0 to not function correctly in some cases.  This is why I suggest renaming the key instead of deleting it.  If you rename it, you can restore it in the future.  You can rename it back immediately after installing the .NET Framework 4 beta 1, but this key will also prevent you from uninstalling the .NET Framework 4 beta 1, so if you do that, you will need to rename it again prior to uninstalling this beta.

  • Renaming this registry key was not officially tested by the Visual Studio and .NET Framework teams, so if you decide to do this, you do so at your own risk and you may run into unforeseen problems.

  • If you delete the above registry key and find that you need to restore it later in order to fix functional problems with the .NET Framework 1.0, you can use the steps in this blog post to repair the version of the .NET Framework 1.0 that is installed as an OS component on Windows XP Media Center Edition and Windows XP Tablet PC Edition.  Alternatively, you can manually re-create the following registry key that is listed in this blog post:

    [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\Policy\v1.0]
    3705 = 3321-3705