BIOS firmware (not software) is stored on the motherboard's CMOS chip and controls the low-level hardware settings and communication. It is what enables a PC to start up in the first place.
It is not, in any way, stored on a hard-disk and cannot be deleted by formatting a hard-disk. You may hear or read references to a tattoo, but that works in an entirely different way, was not used at the time of Win98 and would not create this behaviour anyway.
I would suggest that you first atempt another clean installation of Win98, with all the correct device drivers readily to hand, and see how it goes.