Thinkpads Forum

Harryc wrote:This always works for me, doesn't matter what's on the drive.
http://www.killdisk.com/

dg1261 wrote:The HPA (Hidden Protected Area) is part of the regular HDD space that's been shielded by the controller on the HDD itself. Basically, the controller hides some of the disk cylinders from the outside world.

When any computer boots, the bios queries the HDD controller to get the size and parameters of the HDD. But the bios is going to believe whatever the disk controller tells it, so what if the controller returns fake numbers? If we can manipulate some registers in the controller, we can make the controller pretend that it has fewer cylinders than it really has, and the outside world won't know the difference.

There is a utility called the "Feature Tool" available from Hitachi
(www.hgst.com) that does just that. Set the controller to report fewer than the maximum actual cylinders, and the extra cylinders are untouchable by fdisk, diskpart, BootIt-NG, Partition Magic, et al -- they won't even know the HPA is there. I believe the Feature Tool writes to flash memory on the HDD's onboard disk controller, changing the number of max cylinders the controller reports to the computer's bios during bootup. IBM has wrapped these same controller calls into the bios of recent notebooks to automate setting aside those extra cylinders for its own Predesktop Area.

It's worth noting that the hidden part of the disk can be whatever size you decide to make it, depending on how many cylinders you decide to hide. The Feature Tool allows you to set the maximum capacity of the HDD to be any user-designated amount (up to the real maximum of the hardware, of course). If you set a 40GB HDD to be 35GB, then your computer, and every other utility that looks at that HDD, will believe that HDD is really a 35GB disk. There is no hidden part of the HDD to be recovered or revealed by fdisk, PartitionMagic, or similar third-party utilities because they simply do not believe the rest of the disk exists.

When you use the Feature Tool to reduce the max capacity of the HDD, it "hides from the back". For example, if the HDD really has 2100 cylinders and you reduce it to report itself as having 1800 cylinders, the hidden cylinders are numbers 1801-2100. You can use the Feature Tool to hide and unhide those 300 cylinders, and the data stored in those sectors is untouched. There is a white paper available from IBM that describes the HPA, but IMHO it obfuscates the issue by making it look like the HPA is at the *beginning* of the disk, when in fact it is not. The HPA expands forward from the back of the disk, so the normal partitions you create and use in the visible area are unaffected by manipulations with the HPA.