What if, you know the change in registry key has caused NO BOOT Situation on one of the Machine ? What will be your first troubleshooting steps for a physical machine or a virtual machine ?

Reverting back the registry change.

Good, you know what to do. And this is the only reason Microsoft suggest to take a backup of registry before making any change. Either you can backup entire registry of a specific key. But How to do ?

If it’s a physical machine you need boot-able installation disc and if its a virtual machine you may need ISO in place of boot-able disk. We will discuss exposing boot disk in virtualized environment later on.

I am writing these steps here because it will be common to all the scenario after you are able to open registry [regedit].

Loading Hive

My SBS 2011 machine gave me BugCheck [BSOD] and rebooted with the option to go to repair mode. You can use  below mentioned option to get into repair mode .

OS Booted in Repair Mode

OS Booted in Repair Mode

Once selected “Launch Startup Repair ” ,you will be on the screen

System Recovery Option

System Recovery Option

Click on “Next

Choose Recovery Tool

Choose Recovery Tool

Now you have to Click on “Command Prompt” which will open CMD ,type “regedit” to launch registry editor.

Command Prompt to run registry editor

Command Prompt to run registry editor

Now you can see your current boot drive is ” X ” and registry loaded will be from X drive not from the drive where your actual Operating system is installed. Once you get into REGEDIT you will need to load the registry hive in order to make the desired /required changes.

Registry Editor

Registry Editor

You will not be able to get option to LOAD HIVE unless you select HKEY_LOCAL_MACHINE in the registry editor , once selected click on FILE  and you will be able to see LOAD HIVE and UNLOAD HIVE will be gridout [can’t be selected].

Load Hive

Load Hive

Click on LOAD HIVE it will pop-up will a browser option to look from the registry hive which you want to be loaded. You need to browse till the location . We need our SYSTEM [Type – FILE]  which is located at C:\Windows\System32\Config\ as shown in the below image. select it and click OK.

Loading System Hive

Loading System Hive

While Loading it will ask for a Name so that it can Load the Hive with that Name , name can be anything it doesnot matter simply put whatever is in your mind in single word.

Naming Loaded System Hive

Naming Loaded System Hive

I used TEST ,as it was in my mind while taking the screenshot. You will not find any CurrentControlSet in Test hive, so in order to know which hive is your CurrentControlSet for the Operating System, check Select key . In my case all entry is 1 , however it may differ in your case, check Current key it may be 2 so that means you have to make changes in ControlSet002 ,

Selection Of ControlSet

Selection Of ControlSet

Now your registry is loaded and you can make changes into your registry where ever you like based on the troubleshooting action plan. I had used the same method to change the Storage Controller where I was getting 0x7B BSOD [ BSOD 0x7b on migrating VM from VBox to Hyper-V]

Change As Required

Change As Required

 IMPORTANT

Once you are done with the changes ,never close your registry from the right corner of the windows [Cross Button] it may corrupt your registry . Method to to unload the registry hive is :-
  1. Select “TEST” hive which was loaded.
  2. After Selection , click on FILE
  3. Select UNLOAD , it may give you warning however click on YES . Now your registry hive is UNLOAD.
  4. Again Click on FILE and Select EXIT to close the registry.

 

Physical Machine

Scenario 1

 When Bootable OS media is available . [If you don't have, You can download and use even evaluation ISO and create CD/DVD]
  1. Boot your machine from bootable media .
  2. Go to repair option and opt for command prompt . [Now-a-days not only CD/DVD drive but you can make a USB bootable.]
  3. As you are in repair mode ,command prompt. Your drive is X and Windows Drive is C: which is facing issue and you want to repair registry of that drive.
  4. Type “regedit” and press enter to open registry hive.
  5. Follow the steps mentioned above in Loading Hive section.

Scenario 2 

Another Running Physical Machine is available however no bootable CD/DVD/ISO [Get ready with Screw driver as some physical work is required]

Remove the HDD from the trouble-facing machine and attach it as secondary master or slave [What ever is available however make it sure that machine is not going to boot from the newly attached disk. ]

Virtual Machine

Scenario 1 

Running on VMware [Hard disk is in VMDK format ]

You can attach any disk of your not running VM to a running VM as Data disk.

 

Scenario 2

Running on VMware [Hard disk is in VHD format ]

You can attach any disk of your not running VM to a running VM as Data disk.

Scenario 3

VM running on iSCSI disk [Bootable]

iSCSI exposed disk to the VM in no boot situation can be exposed to any running VM as Data disk to access the files.