In today's (unusually late) DOOM 3 newsbit, a post on
PlanetDOOM confirms from
Activision that DOOM 3 will not run under Windows 98 or Win98SE, but that
Windows XP or Windows 2000 will be required.
If my system hadn't started crashing constantly, I'd still be using 98 myself. Of course swithcing to XP did not fix the crashing, and replacing all the components in my system has still not fixed the crashing. Oh well.
If replacing the OS and the all the hardware didn't solve the crashing problem then maybe you need to upgrade the user