Here is a cookbook approach to zeroing the DiskID.
1... Using Method #3 http://www.goodells.net/multiboot/partsigs.htm#method3
Use a Win98 floppy (or a Win98SE floppy). At the A: prompt, type fdisk /mbr and press ENTER. You won't see anything happen. It just goes back to the A: prompt.
As most people don't have floppy drives, you can also use a Win98 boot CD from...
http://www.allbootdisks.com/download/iso.html
Get the Win98SE_bootdisk.iso. Burn the ISO file with ImgBurn. Use the same method. Type fdisk /mbr at the A: prompt and press ENTER.
2... Using Clear Sig. Download BootIt NG. There is a one month trial usage. Unzip the file and make a boot CD.
double click makedisk.exe, next
dot in I accept the agreement, next
no tick for Registration, next
dot in Mouse Support Enabled, next
dot in VESA Video, next
dot in Partition Work (Don't put a dot in Normal), next
don't choose any Default Device Options (if necessary, these can be chosen in BING), next
leave Registration strings blank, next
select your CD burner drive letter (you can use a CD-RW or a CD-R disc)
Finish
Boot from the CD....
the BootIt NG CD boots to the Work with Partitions window
Using the radio buttons on the left side of the Work with Partitions window, select the appropriate hard drive. (It should be HD 0)
click the "View MBR" button.
click the "Clear Sig" button. Then click OK on the Notice.
click the "Apply" button.
click the "View MBR" button again and confirm the number in the left bottom corner is 0x00000000
click Cancel
click Close on the "Work with Partitions" window
click Reboot and remove the CD
If your cloned WinXP, Vista or Windows7 wasn't booting due to breaking one of the two Rules, zeroing the DiskID will enable the clone to boot. Unfortunately, Vista and Windows7 will need a BCD repair as well, but after the DiskID has been zeroed. Not before.
These methods take less than a minute. That's much better than up to several hours for a repeat clone and there is no need to open the computer to switch hard drives.