Error occured validating
Delete these lines at a beginning of the .vdproj file: Build again - the error is gone.
Basically, if you run MSBuild and see this warning: Then the problem is Visual Studio versioning.
Following the recipe for v184.108.40.206 from MS finally made it work for me: Microsoft Visual Studio Installer Projects Unfortunately we couldn't address all cases of the command line issue for this release as we're still investigating the appropriate way to address them.
What we do have is a workaround that we believe will work for almost all of them.
This means that one project was opened or created in Visual Studio 2010 and then saved or added to an existing 3.5 solution.
I simply searched all files in my project for In my case my solution (VS2008) had a project that was also referenced from another solution (VS2010).
Everything was better now but I got an error when I tried to compile the setup project.