The only real warnings I get are about unsafe mixes of variables, but I have gotten those since making the program, and just have never taken the time to fix them. I don't think that would suddenly cause red underscores though. It really doesn't cause anything negative, as it still compiles, just annoying to see the red.
I figured out the compiler was just having a fit over me using getch() instead of _getch() since it was deprecated, I was to lazy to change it. :/ But doing so made it stop with the lines.