Can't compile content project

Hi !

I just started using MonoGames, by trying to recreate a project I made in XNA.
I created the content project, and added my assets in the “ContentContent” project.

When I try to compile the project, I get this error :

The command “SETX MONOGAME_PLATFORM “Windows” > NUL” exited with code 9009.

Looking on the internet, I found only 1 discussion with the same problem, on the older forum, and for which there was no solution at that time. (this thread is here:

Does anybody have an idea why I get this error ?

My version of monogame is 3.0.1, running it with Visual Studio 2010.professional.

Thanks !