Originally Posted by MarkMcK
If I'm following you correctly, I'd think using Windows "Repair" and the fixmbr function would take care of the Dell boot code.
Yes, it does.
I reviewed the boot code last night. Yes, it looks like it will rehide the MD partition. So I dummied up a spare hard disk I had laying around and tested it (including recreating a HPA) to confirm my interpretation of the boot code.
Both partitions booted as expected, with "normal" boot showing a smaller disk size than "MD" boot--as expected, since the HPA was alternately being hidden/exposed.
Then I used Feature Tool to permanently expose the HPA. It stayed exposed until I rebooted into the "normal" partition. The Dell MBR rehid it.
The Dell MBR will do this regardless of whether the actual MD partition still exists. IOW, even if you use Feature Tool and then wipe/erase the MD partition, the Dell MBR will still rehide the space where the MD partition used to be. That's because the Dell MBR has the boundaries of the HPA hard-coded in the MBR (in that secret, fifth partition table entry). Even if the MD partition is gone, the Dell MBR still holds that fifth entry, so hides/exposes it as a HPA regardless of whether the actual partition is there or not. (Of course, if the partition isn't there, pressing the MD button will expose the HPA and then hang.)
Getting rid of the Dell MBR, of course, solves the problem. 'Fixmbr' is an easy way, but that won't help if you still have a DSR partition you're trying to keep. That's why I was wondering if the MD repair tool would work--to keep DSR without MD.
Anyway, the point of this exercise was to confirm that simply using Feature Tool would not be enough to recover the HPA space. You also have to redo the MBR.