The system won't boot without the jumper or expansion pak. Now, theoretically it could have broken where it still "jumped" the 4mb of RAM, but it's much more likely that it's working fine. I wouldn't worry. If you really want to test it then just buy a copy of Perfect Dark or something. Not only is it an awesome game, but it will tell you at the beginning whether the console thinks you have an expansion or jumper pak. And it's relatively cheap.