Diskpart / Disk Management vs the BIOS

Hello everyone.


I know some of you have seen this issue before and I'd like to get your input on this; I and some others have been working on this in this thread linked below.

Don't Know Why

First Install said:

Another new / clean install is connected to the #1 SATA port of the mobo and set as the first boot device and it was the only HDD connected for the clean install.

Originally the "Movies" HDD was Disk 2 after the others were reconnected but that changed also at a later time.

Edit: I just posted more in the second post down.

This time all the HDD were connected for the clean install, the "Disk #" changes at random intervals and is sometime different from one look at disk management / diskpart to another, it's completely screwy.

This first set of snips is the way it should be and is the way it is some of the time, the second set is from just a few minutes later, sometime the "Storage" HDD is Disk 0 and sometime the "Movies" HDD is disk 0, the C: should be Disk 0 the first snip is the BIOS listing.

Any ideas, anybody?

Here see what I mean, I just now got these.

I'm curious also. Have you tweaked the Plug and Play setting in the Bios.

Hello Bob.


No as a matter of fact, I reset the BIOS/CMOS to default before the first set of clean installs and the only change I've made was from IDE to AHCI, everything is at default.

Thanks for the interest.

I have alway ran mine as "Yes". To run it as "No" I am not quite sure what you would get. I assume the bios would do the settings and Windows would have to accept them. Don't know if that is correct because I have never tried it. It might make a difference in what you are describing.

mjf said:

Yes and I'm waiting for some feedback on the work I did here
Don't Know Why

By all means critic it but I haven't seen a better explanation so far.

Sorry about that mate, I meant to have another look and get some feedback and got sidetracked; good work BTW, I was impressed whan I saw it early this morning but I was on the way out the door.

Is there a way to get the HDD manufacturer serial/model numbers from the Registry?

I'll have another, better look after while.

mjf said:

Yes and I'm waiting for some feedback on the work I did here
Don't Know Why

By all means critic it but I haven't seen a better explanation so far.
I'm saying it's not sata ports but disk signature and a corresponding disk signature entry in the Registry. This was all new to Vista and Windows 7.

What I don' have a grip on is how the disk signature in the Registry keeps changing from one time to the next.

I just wondered if the HDDs could be differentiated in the registry using mfg information.

Thank you for all your input on this!

The Windows OS controls the management of disk signatures. It's an 8 bytes entry in the MBR just like the partition table is.
Windows generates a unique disk signature when the disk is initialized. When the first 512 bytes don't end with 0x55AA Windows does not recognize the existence of an MBR and asks you (or it) to make one by initializing the disk. If the disk is not re-initialized it will keep its old disk signature.
Then this disk signature is associated with a disk number and stored in the registry where I have shown in my snip.
Don't Know Why
When Windows boots it checks each disks' disk signature (in each disks MBR) with the registry entries. If the disk signature is in the registry it gets assigned the matching disk number.

Here is a Windows generated disk signature in my boot disks MBR below and the registry entry above.


Hence you get what you've been seeing. I have not seen this explained before so I welcome criticism so I may learn.

Again this a new important role for the disk signature which didn't exist prior to Vista.