Use gfortran (part of MinGW-w64 or MSYS2).
It is not "Fortran 77 only" but supports the F77 standard perfectly, is actively maintained, runs natively on 64-bit Windows, and is completely free.
hello.exe
Q: My Fortran 77 code uses non-standard extensions
A: Use gfortran -std=legacy to accept old syntax. fortran 77 compiler for windows 10 64-bit free download
Create a file hello.f (.f extension is conventional for fixed-form F77 code): The Short Answer (Recommendation) Use gfortran (part of