Visual Studio Rebuilds unmodified projects

Question

So, as the title reads, I have a VS2010 solution with ~50 projects in it right now. If I make a change to a \"top level\" project that nothing references then VS still rebui

Answer 1

This happens when a project has a file that doesn't really exist.
The project can't determine if the file was changed (because it's not there) so it rebuilds.

Simply look at all the files in the project, and search for the one that doesn't have an expandable arrow near it.