How do I access external HFS+ disk drive after booting into Windows 7

Hatter,
You have nothing to apologize for; it was a quirky combination of circumstances.

I'm not dedicated to Western Digital drives but I'm currently using the My Book in question and a My Passport and I have no complaints about them except for the questionable partitioning choice WD made for the My Book.

As you say, the WD decision to use APM and Apple's decision to support it in recent versions of OS X is motivated by a desire to maintain compatibility with the widest range of old and new hardware and software. It caused me some grief but I suppose the alternatives would have caused someone else some grief.

I'm pretty sure that pre-formatting a drive is a marketing advantage when selling to the mass market where many users have no idea how to partition or format a drive or even what the terms mean.

Anyway, for me, all's well that ends well. Thanks for your interest.

Hatter,
Thanks for your advice. As I understand it, Paragon HFS+ for Windows and MacDrive enable Windows to read from and write to an HFS+ formatted disk. In the long run I may need that "write to" capability, but for now I'd like just to be able to read the disk. Using only Windows with Bootcamp 3.2 I'm already able to read the HFS+ partition on my iMac internal drive; it's only the external Firewire 800/USB 2.0 drive I cannot read. Do you know why I'm now able to read the internal drive but not the external? Do you think Paragon HFS+ is applicable to this problem?

GeekBoy,
Thanks for the suggestion. I did as you suggested and verified the external drive using Disk Utility in OS X. Disk Utility says "The volume My Book appears to be OK."

Here's the cause of the problem and the solution. My Western Digital My Book Studio came from the factory pre-formatted with with the Mac OS Extended--Journaled format (aka Journaled HFS+) and partitioned with only one partition using the Apple Partition Map scheme. Windows, even with Bootcamp drivers, cannot read a disk partitioned with the Apple Partition Map scheme. Using Apple OS X and Disk Utility I repartitioned the disk to use the GUID Partition Table scheme (still with only one partition). I continued to use the Mac OS Extended--Journaled file system. After re-partitioning (which, with Disk Utility, also requires reformatting) I can read/write the disk after booting into Mac OS X and I can read the disk after booting into Bootcamp/Windows. Problem solved; additional background information below if you're interested.

There may be thousands (tens of thousands? hundreds?) of people who know that Bootcamp/Windows cannot read a disk partitioned with the Apple Partition Map scheme but I stumbled onto the fact after hours of experimenting and false steps. Grasping at straws and after exhausting all my other ideas, I decided to reformat my WD external disk in the hope it would clean up some undetected problem preventing Bootcamp/Windows 7 from recognizing the disk. Using Disk Utility to reformat I discovered I had another decision to make: which partition scheme to use (this applies regardless whether you want multiple partitions or only one).

When formatting a disk, OS X 10.6 Disk Utility provides three options for the partition scheme:
1. GUID Partition Table.
2. Apple Partition Map.
3. Master Boot Record.

Simplifying a bit, the GUID Partition Table scheme is intended for Intel-based Macs, the Apple Partition Map scheme is intended for PowerPC-based Macs, and the Master Boot Record scheme is intended for Windows compatibility. Intel-based Macs can read a disk using any of these schemes but can boot only from a disk using the GUID Partition Table. A disk may be formatted with the Journaled HFS+ file system regardless which partition scheme is chosen. But although OS X can recognize and use any of these partition schemes, Bootcamp/Windows can recognize and use only the GUID Partition Table and the Master Boot Record schemes.

More detail about partition schemes may be found at these links (which I discovered only after I had solved my problem using trial and error):
http://macs.about.com/od/usingyourmac/qt/partition-types.htm
http://www.coriolis-systems.com/help/iPartition-3/content/browse-frames.html

Of course re-partitioning and re-formatting the disk wipes out all the data stored on the disk, but I was desperate and Disk Utility does not provided an alternative that re-partitions the disk without erasing it. Coriolis Systems sells iPartition (about $45) which enables you to re-partition a disk without reformatting/erasing it.

Note that Paragon HFS for Windows and Mediafour's MacDrive would not have solved my problem because the problem was not in reading the HFS file system, it was reading the Apple Partition Map partition table. (This is not to denigrate those products; I will consider using one or the other if I find the need to write to the HFS+ partition when I am in Bootcamp/Windows.)

My post on 2/26/2011 explains the cause of and solution to my problem.

GeekBoy,
You were right about the issue with the partition table but since OS X Disk Utility reported the drive "okay," I didn't give it any further thought until I came across the issue again three days later. And I didn't realize your tip had pointed in the right direction until I went back and reread the posts in this thread today. Thanks.