From the fan kit;
"System Requirements: Pentium III-500, Geforce 2 class 3D accelerator,128 MB of RAM"
I don't think the door to the south east (blocked by the guard) can be opened in the demo. When you click on the door, the DK says it can only be opened from the other side, but there may be another way. The only way anywhere else on the level is the pit in the arena at the end of the demo.
