It COULD also be something similar to what I had with my Windows 95 computer. My system is made from parts I had lying around. It's a Socket 7 ATX motherboard with a built-in HDD controller, as was standard for ATX motherboards of that time. ATA-66 I believe.
ANYWAY, the smallest hard drive size I had was a 20.4GB Maxtor drive. When connected, the BIOS said it was 8GB... which is obviously incorrect.
So.... what did I do to get this working right? I went on-line and found really old Maxtor "drive overlay software". I downloaded a floppy image of this software and used a USB floppy drive to create the floppy from the image. I boot the system with my Win98 startup disk and then I swapped floppies and started the setup program of the Maxtor drive overlay softare and installed it to the hard drive. Now, when the computer boots up, the BIOS looks at the boot sector of the HDD and ends up loading the overlay software, which allows me to use the full 20.4GB at once, bypassing the 8GB limit of the BIOS. And Windows 95 installed perfectly and works just fine after that. DOS mode too.