#Once you hit like... P4 and GPUs being common

[ailurinae]

Time for Quake 3 and Starcraft! Netscape Navigator 4!

That said, a PC designed and labeled for Win98 is almost certainly an ATX motherboard, which is what we still use most often for full size PCs (and Mini-ATX is cross compatible):

If the back panel looks like this next image, that is ATX:

The other main option for late 90s would be Baby AT, which are these goofy looking things:

The PC in the pic say Celeron, and the first Celerons were based on Pentium II... there evidently were Baby AT boards made for P2:

(pretty sure those were rare though) The back of the PC would look more like this:

Also possible it is some custom funky motherboard... not sure how much or if Gateway did that. I remember it more in Dell and some HPs... (if there is a big "daughterboard"/the motherboard is in two parts or a weird shape, that is custom)

I found a Windows 98 PC Box, what should I do