What setup are you using to run it DC? I just set WinUAE using the settings mentioned above, then placed a Workbench 3.0 ADF in the DF0: floppy drive, extracted the DIM demo files into a directory on the PC and made that directory an HD. I then booted the emulator via the WB ADF into Workbench, and then launched the demo exe file and it ran fine.