dual boot install q

[dkd brain]

I want to set up a dual boot install, and I am wondering how I should  
format the drives. I have 2 hdd's in my pc, and want to install rhel  
on 1 drive and winxp on the other drive.

Ideally, I would like to be able to use the rhel drive from winxp and  
the winxp drive from rhel...

what would be the recommended drive formats for use in this scenario?

thanks in advance