Win32_DiskDrive.Signature - what's that?

[peternn]

Hi,

I wonder what's the .Signature property of Win32_DiskDrive?
MSDN says just
"Disk identification. This property can be used to identify a shared
resource."

Is this something "fixed" that depends on hardware only, or not?
Will it change after a disk format, incl. low level format ?
Will it change if I move the HDD to another PC, or attach it to another
channel?

So far I only found that on a multi-boot XP / Win 7 box both OS's return the
same signatures.

Thanks.