I don't blame you for taking this measure to be able to play the game you paid for.
However, this statement is not necessarily true:
This is nothing illegal if you have your own original copy of the game, as I have
The EULA (License Agreement) for most games, strictly prohibits modifying the game executable in any way, or using such a modified executable. Whether you own the original game or not makes absolutely no difference as far as legality.
Is there anthing ethically wrong with it? Not as far as I'm concerned. Could you get in trouble for it? Not a chance. This doesn't make it legal, however.