98 Galant Radio says off - won't go away

Hi, I'm having a problem with a radio in a 98 Galant I just bought. The radio said off, so after googling found out about the code and putting the car in the ACC position for an hour. I've tried this 3 separate times, 1 hour, 90 minutes, and then 2 hours. It still stays in "off". It looks like maybe this car had a factory installed CD Changer?? and it's not there anymore, neither are the rear speakers. I'm assuming maybe this is the security if someone did rip out the CD Changer?? Does anyone know? I don't know if there's anyway to fix this or just get a whole new stereo. I called the 800 # Mitsubishi and they had no idea. They told me to take it to a dealer, but if I'm going to pay a dealer all this money, I'd rather just get a new stereo and speakers. but if I can get it working and just have to get new speakers I'd be fine with that. Any help would be appreciated! Thanks!

leave the radio unplugged for a while, then when you plug it back in you should be able to put in the security code.

Thanks So much....so I have to pull the radio out and just disconnect it? sorry, I'm a girl...not much experience in this stuff! I'm pretty hands on, just afraid to really screw with electronics!

Yes

Tried unplugging the radio...left it unplugged for hours, plugged it back in, put it all back together, key in ACC for 1hr 15 mins...and still in off. I guess I'm just out of luck!!!