Recommended Settings for Airport Extreme File Sharing?

I just hooked up a WD My Book Studio Edition II USB Drive to the USB port on my Airport Extreme router. It appears that I can only have one partition on the drive otherwise Airport is unable to share it out.

Can anyone recommend settings that will allow read/write access from both Mac and Windows? It seems like FAT is my only choice here.

If you have a similar setup, please let me know how you set it up and why.

Thank you!