Windows 10: Broken MBR Win 10 no disk

Another computer has stopped working after a power cut. It is an HP Pavilion laptop, originally Win 8 but upgraded to Win 10. There is no installation disk. There is an mbr issue and it can't find the OS. What's the fix please?

:)

 

clone MBR HD to bootable GPT partition?

Hi,

1. You cannot convert mbr to gpt without data loss. otherwise, you can follow directions here:

FROM WINDOWS RECOVERY CONSOLE:

To change a master boot record disk into a GUID partition table disk using a command line

• 
  Back up or move the data on the basic master boot record (MBR) disk you want to convert into a GUID partition table (GPT) disk.
  
• 
  Open an elevated command prompt (right-click Command Prompt, and then click Run as Administrator) and type diskpart. If the disk does not contain any partitions or volumes, skip to step 6.
  
• 
  At the DISKPART prompt, type list disk. Make note of the disk number you want to convert.
  
• 
  At the DISKPART prompt, type select disk <disknumber>.
  
• 
  At the DISKPART prompt, type clean.
  

2. I'd suggest converting your vista drive to a virtual machine, load that up on your windows 10 system and use a program like virtualbox to run it.

 

Convert GPT Disk to MBR Disk in Windows 10


Recently I met an occasion where a Win10 installation on a GPT disk needed to be converted to MBR.
I think my experience may be of some help.

The target system was Win10 Enterprise, installed on an empty 300GB HD. The layout (as reported by "diskpart") was :
Code:

Code:

 Volume ###  Ltr  Label        Fs     Type        Size     Status     Info   ----------  ---  -----------  -----  ----------  -------  ---------  --------   Volume 1     C                NTFS   Partition    297 GB  Healthy    Boot   Volume 2         Recovery     NTFS   Partition    450 MB  Healthy    Hidden   Volume 3                      FAT32  Partition     99 MB  Healthy    System

Basically I followed "OPTION ONE" of Shawn Brink (the author of the original post).
Steps 1-3 were straightforward.
After clicking "Convert GPT Disk to MBR Disk" in Step 3, a warning poped out :





Click "OK" to dismiss, then proceed to Step 4.
After clicking "Apply", another warning appeared soon :





Click "Restart Now" to proceed.
The restart triggered the conversion before loading the OS.
When the conversion was completed (in just one or two minutes), the system was restarted again.
But this time it CRASHED : some error message saying OS not found.

This is normal, because the conversion tool did not mark the system partition as "bootable".
Now :

1. Boot the target system with the Win10 installation media (DVD/USB etc).
2. Select language & click the "Next" button.
3. Click the "Repair your computer" link.
4. Click the "Troubleshoot" square.
5. Click the "Command Prompt" square.
6. At the command prompt, invoke the "diskpart" tool.
   • Locate the target partition by using the "select" and "list" commands.
   • Execute the "select partition x" command, where x is the target partition number.
   • Execute the "active" command to mark it as "bootable".
   • "exit" the "diskpart" tool.
7. "exit" the command prompt.
8. Click the "Startup Repair" square. The system will restart after the repair.
9. Done.

After the fix, the layout of the target disk looked like :
Code:

Code:

  Volume ###  Ltr  Label        Fs     Type        Size     Status     Info    ----------  ---  -----------  -----  ----------  -------  ---------  --------    Volume 1                             Partition    450 MB  Healthy    Offline    Volume 2                             Partition     99 MB  Healthy    Offline    Volume 3     C                NTFS   Partition    297 GB  Healthy    System

Finally, a couple of remarks :

• The time required for the "Startup Repair" step varies on different systems. For the 300GB disk mentioned above, it was finished in less than a minute. On another case with 1TB HD, it took nearly 3 hours of heavy disk read-write to complete the operation.
• One downside of the method is worth notice : almost all of the functions in "Advanced startup" ("Start" -> "Settings" -> "Update & security" -> "Recovery" -> "Advanced startup") were gone after the conversion.

 

Convert only one partition on the disk from MBR to GPT

Step 2
Convert MBR to GPT without data loss