Stephen,
First of all, you needn't have purchased DoA. It's available free via download from iEN. The most recent version is 2.75r2 so assuming your copy is out-of-date, it's probably best to d/l the new.
ftp://lists.ient.com/pub/Dawn/2.7.5
Be advised there is the 2D version (which can be played using even the most basic sound/game card) as well as the 3D version (which would require a 3D video card, faster CPU and more RAM). What I'm thinking is that you may have installed the 3D version and it requires SVGA drivers installed and/or your monitor is only VGA)
If you continue to have difficulties; post at (iEN Dawn of Aces UBB Forum)
http://lists.ient.com/cgi-bin/Ultimate.cgi
The DoA community is chock full of techno-wizards who are always ready, and more than willing, to assist new recruits.
VBR
Rod a.k.a. Rosbud