(re: Shadow of Darkness) there is a fellow who has created timer fixes for the most critical parts in sierra games:
http://geocities.com/belzorash/
however, it does not fix everything; if you want the game to run as it was intended, use dosbox 0.61. It supports general midi now, the sound and music is great in this version; better than i could get it working in VDMSound, and theres absolutely NO timer related problems (in qg3 & 4 the whole stamina thing was messed up when you did certain things ie cross the rope in the cave).
you just need to make sure you set up dosbox right; they say it varies from pc to pc but i found running it at about 4500-5000 cycles would give me pretty much full speed. you’ll also want to enable opengl mode unless you want a slowfest while playing in windowed mode.