If you ever want to divide a drive into two partitions, one formatted as Mac OS Extended (HFS+) and the other as FAT32, and to be able to access the FAT32 partition from Mac OS X and Windows, just make sure you set the FAT32 partition as the first one on the drive when you partition it with Disk Utility.

This may be evident to some people, but I was a little surprised that my first attempt at it failed.