Saturn help

I recently purchased a pre-owned Sega Saturn from E-Bay. The unit was in the original box and seems to be in good cosmetic condition.

However on closer inspection, in the back right of the unit, there is a SILVER screw/bolt, as if the unit was opened up.

I hooked the system up, put a game in the drive and fire it up. Up comes the Saturn screen, then the system goes to the 'set-up' screen, and up pops the message that says something of the following:

"The CD is not compatible with this system".

I have tried multiple games/discs all with the same result.

I tried putting a Sega RAM Cart in the slot, still the games do not boot and I get the same message, that the disc is non-compatible with the system.

I know its not my games, for they all work on my other Saturn console.

On looking at the onboard RAM data, I did notice a game save of Radiant Silverstorm, which is an import (as you all know).

What I'm thinking, is with that screw/bolt in the back, that this unit was 'modded' with a mod chip to play imports.

However, I can't get anything to boot up. But I have no imports to try anyway.

I emailed the seller, and he thought that the unit was modded, but was not sure. And he has no idea how to get it working.

My questions:

Is this unit defective?

Does anyone have any idea or any suggestions on getting this thing to work?

The unit is NTSC, says that on the set-up screen.

Do you have any other forums or Saturn experts who may have a solution?

Thanks in advance,

Have you opened it up yourself? The modchip doesn't play imports anyways, only back ups. if he had a Region swich installed, then thats different. But open it up and make sure The ribbon is firmly in the slot it goes in and that its pins are all connecting. Maybe if he had a mod chip, he took it out and put the ribbon back to the original spot but didn't do it just right. I dunno, Mal is good with this stuff. He'll help im sure.
If it says "Game disc incompatible with this system.", then the Saturn is set (whether at the factory or by a modification, the effect is the same) to a different region than your games.
sounds like it's either japanese (but if it's in a black case I doubt that), modded to japanese only, or has a regions witch. If it's got something weird in the back that might be the region switch. Give the system a shot though with a 4in1 in there if you have one to see if it's got any other problems than being a different region. If worse comes to worse, you can get someone who knows what they are doing to perform a mod to either return it to us for you or to install a region switch.

Edit: This may sound stupid, but have you looked in the little compartment that the vcd card addon goes in? It seems like a handy place to put a switch if you never plan on having a vcd card so it may be there.