Hardware :: 500GB WD Portable HD From The Apple Store

I recently got the 500GB mini WD MyBook from the Apple Store. It came pre-formatted for mac. Now here's the problem. I reformatted the main partition into FAT32 because I wanted to use it on PCs as well. I loaded it up with files from my other 500GB HD (which was the big non-portable version of the MyBook) which I proceeded to wipe out and sell. So all the files are now on my portable one. Now here is the problem. When I plug it into my mac, it works fine. No worries there. But when I plug it into any PCs it will not see the partition. I have to manually initialize it and it seems like it wants me to format it before it will even assign the drive letter (from what I saw in Disk Manager in the control panel).

Disk Utility seems to default to HFS on the root of the drive, but it does correctly identify the main partition as FAT32. I have no idea what to do. Ideally, I'd like to have the drive be used on PCs and Macs, though I must err on the side of caution and keep my files preserved at least for a few months until I come back home to the US and gain access to my additional storage space.