rtcvb32: EOB1? I will assume it's Eye of the Beholder.

Is this a GoG archived game or are you doing this yourself?

GoG's games should be preconfigured to run, but if you're doing it yourself you might need a little bit of overhead and work first.

I suppose worst case use Alt+Enter to change between full/non-full screen as appropriate.

First guess is the resolution isn't compatible with your video card and/or monitor, and you might have to change the scaling options. You'll have to go into the configuration file that's most likely named dosbox.conf and edit it.

Off hand that i remember, it will probably be 640x480 resolution, though it could be 320x240; Either one it's probably 16color. Upscaling will be 2x, 3x or 4x, that may or may not have the HQ filter (that tries to make it look less blocky but takes more CPU power)