I downloaded Eye of the Beholder a couple weeks ago, and today is the first time I really got to play it. i tried, and i am getting a game screen, but it is a small window (not a complete screen), and there is no sound. Can someone help me?

GoG uses DOSBOX for its DOS based offerings, and the configuration is done the same way as normal for DOSBOX.

For the size of the window, scroll down the DOSBOX configuration file (it will be in the game install directory, look for a .conf file) and look for the part that starts with [render], there will be a line that says "scaler=normal2x" or something like that. This determines how large the game window will be scaled. The basic size is 320x200, which is what you get if you pick "none"; options with "2x" will give you a 640x400 window and "3x" will give you a 960x600 window (this is about a quarter of the screen on a 1080p monitor/TV).

Comments on Let's Plays for games of this era seem to consensus that it's best to stick to the normal2x or normal3x scaling options; the other options (except "none" of course, but that's really tiny) attempt to "enhance" the image but don't really do that great of a job of it :)

You can also full-screen the game by hitting Alt-Enter. (I'm personally not a fan of full-screen mode gaming on Windows, primarily because of how the OS handles such; it works okay on Linux though)

Note that screenshots (Ctrl-F5) always appear to use the original scaling of the game, even if the window is larger or you're running full screen.

For the sound I've found this post at Vogons. GoG's normal DOSBOX config appears to be using sbbase 220, irq 5, dma 1, hdma 5, btw (I'm not sure why they changed it? as a stock dosbox-0.74.conf file uses irq 7).