I opened my vs2010 solution with vs2012 but it didn\'t make any conversion as from 2008 to 2010 was happening. So my solution still remains the same as 10 label on it. when
In my case, I had some Visual Source Safe stuff (my project was created with Visual Studio 2003/2005, yes, very old!)
Once I manually removed the VSS stuff, the conversion succeeded. PS: I know it's about VS2010, but maybe this helps others.