I do a multiboot thing myself,
Pentium III era mobo with 2 IDE HDDs.
I have Windows 98SE, Windows XP, and Linux Mint 7 all living peacefully (it's always useful to have some linux distro to unfuck file system and bootloader problems imo).

The way I set it up is to only have one drive connected, let's say primary--install Windows 98SE.
Then disconnect primary and only connect secondary--install WinXP.
Connect both drives and then install the linux distro. Linux Mint 7 happens to use GRUB and installs+configures the whole thing automatically, very convenient for switching between the OSs.
I reserve 6 GB for LM7 and its swap, but you could probably get away with 4.5 without much issue, so long as you don't really add anything.

I will say, LM7 is a bit heavy for that P3 (866 MHz), if you're on a much weaker processor, an older or at least lighter distro might make sense.

I usually do 2 methods for dual booting. 1 is mobil racks (IDE version):

With this I swap drives depending on which OS I want to run. For my XP/Vista build I use a Chieftec CMR-225 with 2.5" drives and I disconnect (pull) the one I'm not booting.

The other method is xfdisk:

https://youtu.be/RvI8Q0uaihI

Then hide the OS partitions from each other. NT based systems still see them all so on the first boot I just remove the drive letter from the W98 partition.
I usually use this for 3 or more operating systems (DOS 6.22, Windows 9x and 2k/XP).

GemCookie wrote on 2025-08-08, 07:14:

I tested both Windows 95 and 98 SE on this motherboard, but had absolutely no luck running them. Most of the time, the display a […]
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I tested both Windows 95 and 98 SE on this motherboard, but had absolutely no luck running them. Most of the time, the display adapter would conflict with System board extension for PnP BIOS, making GPU driver installation impossible. I somehow fixed this on two occasions; however, installing the graphics driver would then make the system unusable. ForceWare 66.94 and 71.84 made it reboot right after the splash screen, while 77.72 and 81.98 triggered a Windows protection error.

I would also get Runtime error 202 followed by a system hang from time to time, especially during software installation. I encountered a similar issue on a Haswell laptop; I solved it by adding the following lines to system.ini:

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1[vcache]
2MinFileCache=1024
3MaxFileCache=1024

I got 512MB memory / gf6800 vga / 80GB IDE / and totally disabled sata from bios, successfully installed win98se with 81.98 driver, without any modification.
I believe failed reason is sata, even compatible mode is not working.