How do I fix an "Invalid license data. Reinstall is required." error in Visual C# 2010 Express?

I am using Visual Studio 2013 and I have the same issue but it occurs when I try to open a solution that was made using Visual Studio 2010.

The solution for me is to open the solution file (.sln), using notepad and change this line:

[# Visual Studio 2010]

to this:

[# Visual Studio 2013]

I just right-clicked, and opened with Visual Studio XXXX (in my case 2015). Then save it. Done.

I have the same problem with Windows 7 Pro. Have tried everything suggested by the Microsoft people, including uninstalling, cleaning up, reinstalling both from the web installer and the VS2010 Express iso - with the same result every time.

To say it's frustrating is an understatement and the disinterest from Microsoft in fixing what appears to be a common problem (you can find lots of search engine 'hits' for the problem, none for a solution) is quite unbelievable.

Since this is virtually a virgin Win7 install, the only conclusion is that MS have broken their licesing checks again (why check for a license on a free product?).

Edit: Following further investigation I have concluded that the advice given by Microsoft is useless and does not attempt to diagnose the problem. It simply assumes a corrupt installation source. I believe that the problem is in fact corrupt permissions/ownership of registry keys. HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Licenses and subkeys needs to be owned by SYSTEM with admins having full access. On my affected system the owner cannot be displayed and no permissions are shown when viewed by admin.

I don't have the definitive fix for this so far, as I cannot adequately edit the permissions for the affected registry keys.

Re-installing Windows is an almost certain fix, but also an extremely drastic one.