Yes you can install 98 on that drive. You would probably want to disconnect the XPdrive just so 98 doesn't try anything funny, even though it's NTFS. Unless you use third party partitioning software you will have to dual boot using BIOS. i.e. Boot to C: or Drive 0 for XP and boot to D: or Drive 1 for 98, assuming that this is how the BIOS sees your drive scheme.

No, you'll actually need to boot with a boot manager, as win9x requires to be on the first primary hdd, and the first partition on that drive.

Really! I am dualbooting right now with a similar drive setup without a boot manager. I have 2000 SP3 on my RAID array and a 40 gig on channel 2 as master with 98 on it. All I do is go into the BIOS and tell it to boot to either RAID or Drive 2 (starts at 0). As long as you disconnect the other drives (during OS install), and your bios allows it you can have 4+ drives booting whatever you want. I also have Mandrake 8.2 on drive 0, so i guess that's triple booting.

when doing dual boot you should always install the lowest OS first. thus you should install 98 before installing 2000 to another drive or partition.
Boot managers suck and they cause more problems then they solve so you should always try to avoid them at all costs.
installing 98 when you have 2000 installed can seriously hose your system up.
S

Well won't work unless you have an MS-DOS boot partition on C:, just as I figured.