How to fix visual studio 'projects out of date' message each time I run it

Question

I have a visual studio (2005) solution file with 70 projects.
Each time I press F5 to run it, it tells me that 4 of the projects are out of date, and asks me if I want to re

Answer 1

I had this problem and it turned out I had a header file added to my project but that I had deleted from the disk. Removing the non-existent header file from the fixes the behavior.