Windows XP plain -> SP3 is not a problem. I’m not so sure about 98 -> 98 SE. This one, I personally would install from the 98SE installer.

Put everything onto one disk. Splitting it up onto multiple disks just makes it messier.

I have a Pentium 4 board with the normal two IDE and two additional SATA ports as well that I dug out recently (ASUS P4P800), and I can use all six drives there. I have the boot drive on IDE, though. If you want to boot from SATA, which sounds like the most preferable option for you, you will need to set it to legacy mode, and you are right that this will likely limit the amount of available drive ports, but who needs so many drives in such an old system anyway?

There's no path to upgrade 98 to 98SE. It's not a service pack.

There is a neccessity to install Intel's motherboard chipset drivers for those P4 boards on Win98SE however. Neglecting to do so will either have hardlocks or really slow AGP performance when games are played.

You can at least try to limit the memory Win9x has access to with msconfig for more stability (assuming you can boot to 98 at all).

There was 98SE OEM Eng iso on archive.org. Can't seem find it now. OEM versions were bootable!

stef80 wrote on 2022-04-22, 06:51:

There was 98SE OEM Eng iso on archive.org. Can't seem find it now. OEM versions were bootable!

You can still find it on LINK REMOVED
It's been up for a while and not hidden so I guess it's not illegal.
LINK REMOVED

Ringding wrote on 2022-04-22, 06:04:

Put everything onto one disk. Splitting it up onto multiple disks just makes it messier.

I disagree. If you have two operating systems on the same disk and need to reinstall Win98, it will overwrite the boot loader of WinXP.

Using two separate disks and selecting which one I want to boot from using the BIOS startup key (F11 in my case) is much easier. And this way, you can reinstall Win98 as much as you like since it cannot read the NTFS partition that WinXP resides on, and therefore can't mess up the boot loader.

bootloader (MBR) is usually not on OS partition, but on first sector of partitioned disk. And you usually want XP bootloader to handle Windows98.
On 512-byte sector disks, first 446 bytes is actual bootstrap.
To be precise:
446 bytes – Bootstrap
64 bytes – Partition table
2 bytes – Signature

stef80 wrote on 2022-04-22, 08:07:

bootloader (MBR) is usually not on OS partition, but on first sector of partitioned disk.

You're right about that. From my experience, if you install Win98, then WinXP after that, everything works fine and the XP loader picks up Win98 correctly and allows you to boot that OS.

However, if you then re-install Win98, it will overwrite the XP boot loader and you will only get Win98. This is why I prefer two separate disks.

I undersand. Also, you can try to repair MBR from XP Recovery Console.

Joseph_Joestar wrote on 2022-04-22, 08:12:

You're right about that. From my experience, if you install Win98, then WinXP after that, everything works fine and the XP loader picks up Win98 correctly and allows you to boot that OS.

However, if you then re-install Win98, it will overwrite the XP boot loader and you will only get Win98. This is why I prefer two separate disks.

You are correct. I once had to fix the NT bootloader after installing 9x and documented the process here. It is doable and not rocket science. There are advantages and disadvantages to both approaches (single disk vs two disks). I think I agree with you that two disks are usually simpler and safer, unless you simply have no room for another disk (like on a laptop).

Thanks all! A lot of helpful information in here. I got it to POST so that's good news, had to replace the CMOS battery on the motherboard though. I found another IDE drive, a Maxtor 18.2GB. Since I'm not a pro at this yet, I'm going to start by trying to install Windows 98 on that and keep them on separate disks in case I screw something up and need to re-install. Once I figure out how to get everything dialed in maybe I'll look into starting over with a single disk dual boot on the SSD, or at least look into replacing this gigantic hunk of loud spinning metal for something flash-based like an IDE CF adapter.

I think focusing on Win98 now and worrying about XP later is a smart idea. Your going to have to do a few re installs as you get the hang of it anyway.
For partitions I'd keep c:\ at 4GB or below, typically for Win98 I set it as 2GB. This ensures Win98, scandisk and XP's boot loader will all work as larger drives can cause problems. Every other partiton can be whatever size you wish