.Net Framework 3.5 SP1 on Windows 7 not recognized by installers

Windows 7 Ultimate RTM already comes with the .Net Framework 3.5 SP1 preinstalled. However, some installers like the Azure tools and SDK 1.1 seem to check for it and fail:

Windows Azure Tools for Microsoft Visual Studio requires .NET Framework 3.5 SP1.

Since the framework is preinstalled there seems to be no way to reinstall or repair it (see also).

Installed:

• VisualStudio 2008 SP (9.0.30729.1)
• VisualStudio 2010 RC (previosly beta)
• Windows\Microsoft.NET\Framework contains folders for all 1.0, 1.1, 2.0, 3.0, 3.5, 4.0

Any ideas on how to make the installers recognize the 3.5SP1 framework (without reinstalling the OS), or maybe to somehow reinstall it

Solution 1:

As described here:

The promlem has been fixed after HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\v3.5\SP was set to 1.

More info here too (linked in the page above):

Also could you check the following two registry keys and let me know what the values are?

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\NET Framework Setup\NDP\v3.5\SP

And

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\v3.5\SP

To get pass the install error, if the value of the registry is 0, set it to 1.