Hard disks contain a signature within the MBR starting from address 0x01B8 (through to 0x01BB). Using a hex editor, Tinyhexer for example, it is possible to view the disk signature of a physical device or a hard disk image. If viewing a disk image I recommend that you extract the first sector and open that in Tinyhexer - opening a full disk image will take some time.
To extract the first sector of a disk image file or physical disk use dsfo.exe (part of the dsfok). Open a command prompt in the directory containing dsfo.exe and -
To view the disk signature open C:\mbr.bin in tinyhexer and goto Edit > Goto... and enter 0x01B8. The disk signature is a four byte value starting from this address - see table below.
When creating a disk image using the method described here (using mbrbatch.cmd) the disk signature will be empty (zero byte value 00 00 00 00). It is possible to add a disk signature by overwriting four bytes from hex address 0x01B8 in tinyhexer and saving the changes, then writing the extracted sector back to the disk image.
For a detailed breakdown of the Windows 2000/XP Master Boot Record (including disk signature) see here.