It doesn't. There has to be a ._main.c file for there to be an error coming from it. Besides that you don't search for a project file using Windows when the program that's giving the error supposedly has the file loaded already.
All you have to do is check the list of code files for the project in whatever program you're using to compile the game. There is a file actually NAMED ._main.c
(I might add that Windows search couldn't find its way out of a paper bag since Vista really. I wouldn't rely on it.)