I've noticed, at least with Fallout 1's high-res pack, if you set it to automatically use your desktop res, it will use a widescreen resolution. But if you try to use a custom res in anything but 4:3 it won't. My 24" is 1920x1200 and it actually works in that res, it's just too bad that I can't stand playing at that res because it's just too small.

This error apparently rears its ugly head with some combinations of ATI Radeon cards and widescreen hardware as well - in my case, with the Radeon 2600 HD + widescreen on my laptop. The fixes in the thread don't seem to work, but installing the sfall patch (http://timeslip.chorrol.com/sfall.html) and setting Mode=4 in ddraw.ini did. You may need to tweak the resolution settings in there a little, too.

Renaming ddraw.dll got it working for me, thank you very much.