I second the DOSbox recommendation. Much the same way you can use an emulator to play N64 games on your PC without booting into a platform that's designed to allow for such a thing, the same principle can be applied to old DOS games. Just install the emulator, and things should work. I've had good luck with DOSbox in the past, the one issue I've had is that games that try to play sound through the PC speaker tend to be completely unplayable (all the I/O blocks whenever a sound plays) unless I disable the sounds (which is no big loss, since PC speaker noise is pretty annoying anyways).
Alternately, I think any mainboard based on the nforce3 chipset will let you use relatively modern components in your PC and still offer driver support for Win 98. Suspiciously, nforce4 drivers do not seem to exists in Win 9x flavor, so you might be out of luck if you want PCI-e for your system.