The true starting point for PE executables is AddressOfEntryPoint in the PE header, with a few parameters pushed on the stack. WinMain is a compiler abstraction; it is not looked up by name.
You can't code in a high-level language like C without working with abstractions. Whether you look at the main() level or the WinMain() level, there will still be library initialization hooks running before your end-user code gets to run.
I'm gonna upvote your comment as you are one of the few people in YCombinator who seems to know what they're talking about. Good job catching that, and you're right. The PE Header contains the entry point. (And the MZ Header is potentially a 2nd entry point left in for DOS Compatibility purposes)
The rest of the people here talking as if C is some sort of ultra-portable magic language need to learn about the low level details that differ between OSes.
My primary point remains however, the easiest and most straightforward way to interface with Windows libraries is through C++ and C#. Even C itself is a high-level language built on top of abstractions built by compilers and linkers.
You can't code in a high-level language like C without working with abstractions. Whether you look at the main() level or the WinMain() level, there will still be library initialization hooks running before your end-user code gets to run.