CreateFileA, the mother of all self-checks

I don't know if I understand all this topic, but relatively at the .bak method, there is a well knowed way to bypass the CRC-check on disk : simply leave the original exe as it is and start the patched one, renamed, in the same folder... What more is needed ?

GetCommandLine, GetModuleFileName and the other derivatives can give you the filename of the the exe that's running.

You're assuming that the filename was hardcoded somewhere; which is usually not the case.