Partitioning question

[moocow2024]

I am wanting to run a dual OS on my dell machine, XP and Mint. I have a 60 gb HD on the dell laptop and I'm not exactly sure what i'm doing when it comes to partitioning. What all goes on the partition for mint? i have seen suggestions of 10 and 20 gigs, but if the OS only takes up a few gigs why would i need to partition that much just for the OS? I was assuming that most of my files would be stored on the last partition that is shared between operating systems. if someone could explain exactly what goes on that partition and maybe give me a suggestion on how you would do it, i would greatly appreciate it.