I converted a project recently from XNA to Monogame on a Windows 7 machine. I am unable to open the solution on 8.1 due to the content project. I created the content project as a monogame content project, but it looks like it’s still referencing XNA somehow? Has anyone had this issue?
AFAIK there is no monogame content project (in visual studio) 
Maybe it is a normal xna content project?
That is the old MonoGame content project. It depends on the XNA content pipeline and only had extension processors which knew how to generate content for iOS, Android, Win8, etc.
In the latest development builds we’ve extended the project templates to use the new MonoGame content pipeline via the new Pipeline GUI tool. This doesn’t have any dependency on XNA.
Ahh, I see. So this will be available in the next release then?
I don’t know much about the releases, but you can use this in the meantime with VS2012/13:
I see that you are using VS2010, so you should be good to go with the WP7 SDK too.
You can use Monogame Pipeline(external tool in development build of monogame framework ) to compile content, but it didnt support custom content processors.
It actually does.
/reference:Your.Content.Pipeline.dll