What I would do:
Connect the second hard drive and make sure that the first hard drive is seen by the BIOS as the boot drive.
Unplug the first hard drive.
Install Windows 98.
Reconnect the first hard drive and, just to be sure, again check that the first drive is the BIOS boot drive.
Install linux, placing the Grub bootloader on the MBR of the first hard drive.
If you're lucky, the linux installer will have created boot entries for both Windows XP and Windows 98. If not, you will need to create them in /boot/grub/menu.lst:
For Windows XP, something like:
title Windows XP
root (hd0,0)
makeactive
chainloader +1
and for Windows 98, something like:
title Windows 98
rootnoverify (hd1,0)
map (hd0) (hd1)
map (hd1) (hd0)
makeactive
chainloader +1
if this doesn't work try rootnoverify (hd1)
This assumes that you are using Grub and not Grub2. If you have selected a distro that uses Grub2 then it requires some other exotic incantation, that I'm not familiar with. Mageia uses Grub as default (with Grub2 available as an option). OpenMandriva uses Grub2.
Caveat - it's been a very long time since I touched Windows 98 and so this may be out-dated. :huh:
Jim