Dats simple!
U need 2 hardisks for total 8 primary partitions!
1. Create a boot partition with ranish partition manager!(Say 10 Mb)
2. Create a swap partition (I donno whether the two linux can use the same swap partition,well check it out urself)
3. Create two ext3 partitions and a two windows partition!
Now save the partitions
4. Install 98 then Xp!
5. Install Mandrake on one of the ext3 and then RH9!
Please remember to format the corresponding partition when the OS is being installed!
Just incase the last linux distribution you install does not detect the other linux distribution, its simple to fix that by adding its entry to the LILO/GRUB boot loader. Check this PCQuest article -
First install Win98, then WinXP, then first Linux distro with GRUB.
For every subsequent distro you install, don't install GRUB. You will have to configure it manually in the first distro Follow the link ujjwal has given
No need for two hard disks. All you need is two primary partitions. One for WIndows XP and 98 and the other for Linux Boot loader (GRUB or LILO). Only <100 MB space is needed for the /boot.