The long-story-short: for formatting large disks for the FAT32 file system, use Fat32Format from this place.
This week, I bought an AirPort Extreme Basestation (which up till now is a bit of a disappointment, I must say) and one of the goals was: to connect a large USB disk to the AirPort and then share this disk for the Verhagen's Home Environment.
After connecting the disk to the AirPort, it gets recognized immediately by the AirPort and the option for sharing the disk is offered. However, in my Windows 7 notebook, the disk does not show up in the network environment. After consulting the log in the AirPort, it turns out that the disk does not show up because the file system on this large disk is NTFS (of course). However, NTFS is not supported on the AirPort, we need to change it to FAT32.
After googling a bit on how to format a (large) disk for FAT32, I ended up on the Softpedia-page that the upper link points to. Great tool, formatted 750GB in under one minute... Great!