Most likely you cant boot off the card, hence the no "boot other
device" option.

I still think that if you can edit the boot.ini file you can get this
to work. You have 2 onboard IDE devices and 2 card controlled devices.
IDE1 - /dev/hda IDE2 = /dev/hdc, IDE3 (firs card IDE device) -
/dev/hde, IDE4 = /dev/hdg. So your boot.ini file should read somthing
like mulit(5) disk(5). Simply stated, the boot HD on the controller
card is the 5th ide device reckonized by the BIOS.

All you really need to do to make this work is put the boot loader on
another media. Like you said you can add another HD and put the
NTDETECT, NTLDR, and boot.ini files on it and leave the rest of the OS
on the HD connected to the controller card. Your BIOS supports USB
boot, so get the smallest flash card you can find, and a cheap flash
card reader and put the boot loader on that. You can use the NT
loader, LILO, grub, etc.. If you dont have a lot of experiance w/ boot
loaders, find one called GAG. GAG is a great, low end boot loader
thats very easy to configure, if youve never configured a boot loader
before.

Good Luck