If you're using XP, format it FAT32. That way you'll be able to read AND write files from your Mac partition. On NTFS you can only read. Also if you want to use Boot Camp with VMware you need to make the Boot Camp partition first.
Look this is the main explanation:
FAT32: use for windows xp/2000
You can Read and wright
you can use Vmware fusion and parells
You can format with FAT32 when you have 32GB or less
NTFS: you have to use this for vista and for harddrive partions bigger then 32GB
You can only read form your mac side
You cant use parells or VMware Fusion
Q: so how do you have a vista bootcamp partion and run parells desktop or vmware fusion.
A: YOU CANT
You can... for free: http://www.ntfs-3g.org/YOU CAN
It's called Paragon NTFS for Os X. A simple driver that allows Os X to write to any NTFS partition. Only problem it costs 40 dollars