Descent 3 always switches to the 640 x 480 resolution in its main menu and while starting up.
You can use command-line switches to change the resolution inside the game (
www.dateiliste.com/en/descent-3/67-getti...nd-line-options.html), but this won't change the menu. While playing, you can increase the displayable size with the + and - keys next to the backspace key.
I'm afraid the only solution I can see is that you somehow need to tweak your system to display 640 x 480 correctly.
Or you could probably use Alexi's patched MAIN.EXE version. That version shows the menu in 1024 x 768 to avoid that D3 re-arranges the desktop icons. Disadvantage is that the menu looks terrible, at least here.
I you'd like to give Alexi's version a go, I will have to find it again first.
