Complex Retro Multi Booting Dell Dimension 4100

My Dell Dimension 4100 has been rigged up to the gills with hardware, and as such I've tried to load it up to the gills with operating systems. This has proven to be difficult for me, so I figure similar setups might be difficult for others, so I'm writing down what I've got working (also, I keep forgetting how to boot all the options, as they are not always obvious).

What I have:

• Dell Dimension 4100 - Upgraded with ATi 9550, PIII 1GHz, 512MB PC133
• IDE Primary
  • IDE2SD (C:) (sda)
• "Rosewill RC-200" (sil 8xxx) 2x ATA RAID Card
  • 160GB HDD (storage) (D:)
  • 40GB HDD (E:)
    • Windows 2000
    • Xubuntu 18.04

What I want:

• default boot: IDE2SD (works)
• 160GB MBR: Win2K bootloader (installed, not fully functional)
• 40GB MBR: Xubuntu bootloader (GRUB2) (works)

The Problem

Windows 2000 will not boot if the bootloader is run from anything besides the first disk, regardless of what disk your system is configured to boot from. In my case, that means that Windows 2000 cannot be booted unless the active partition of Drive C: contains the NT bootloader. This is a problem because C: in this case is a removable SD card, and thus will be swapped in and out to run different operating systems. Part of why I wanted 2K installed to the HDD, rather than an SD, is for "rescue" type purposes - to manipulate a damaged 98SE install on an SD card, for example.

Unfortunately, the only two ways I can get 2K to boot are:

1. Install the NT bootloader to the SD card
2. Disable the SD card so that D: becomes C: and the bootloader is now on the first drive

For now, I'm using 2. For some reason, I cannot get 2K to overwrite the remnants of GRUB in the MBR of D:, so I have to use the AIO boot floppy to boot the first partition directly.

I don't believe 2K can boot from floppy.

The Rescue mode on the 2K boot CD can be used to fix the bootloader when disk configuration changes.