well it depend on what you want to do.

if you are making a 3dfx pc for playing sum of the first 3dfx glide games you will want:

voodoo Graphics or voodoo rush or voodoo 2
a good socket 7 motherboard
pentium 1 mmx 200mhz or a amdk7 200mhz
64 to 128 megabytes edo or pc-100 ram
sound blaster awe 16/32/64
about a 10 gigabyte ide hard drive
windows 95 or 98
a 16x speed cd-rom drive

if you want to play newer 3dfx games you will want:

1 or 2 voodoo2's or a voodoo 3 or a Voodoo Banshee
a good slot 1 or slot A (AMD) motherboard or socket 370
pentium 3 500mhz to 1ghz or a AMD Athlon 500mhz to 1 ghz
sound blaster 128 pci or sound blaster live
about a 20 gigabyte hard drive ide
128 to 256 megabytes of pc-100 or pc 133 ram
windows 98 or windows 2000
24x speed cd-rom drive

and for the newest games past 2002 you will want:

voodoo VSA-100 Series video card
a good Socket 478 or AMD Socket 462 A motherboard
pentium 4 1.7ghz to 3ghz or a AMD Athlon XP 1.5ghz to 3ghz
512 megabytes to 1 gigabytes ddr ram
sound blaster audigy
50 to 100 gigabytes ide or sata hard drive
a 24x speed cd-rom 8x dvd-rom combo drive  
windows xp or win 2000


note voodoo 1 and 2 haft to have a 2d card and a pas though cable to run, and this is gust guide line not what you haft to get.  i hope this helps those that are building  a 3dfx gaming pc