Just look up any Falcon Northwest PC ad in that era (do you want '98? '99? 2001?), and spec as close as you can.

Generally I would stick around these specs:

500Mhz Pentium III Intel CPU or higher
Voodoo 3 3000 AGP video card (16mb)
128mb-256mb of PC100/PC133 SDRAM
20GB-40GB PATA 7200rpm hard drive
Sound Blaster AWE64 or Live! sound card
8x DVD-ROM drive
300W-ish power supply
Windows 98SE