Windows 10: I messed with my BCD and now I bluescreen on startup.

I messed up my bootloaders bad. I’ve got an old Acer AspireX running windows 10.Tuesday night, I tried to install the update for 21H2 and for whatever reason, it broke something with my boot files, causing windows to get stuck in the “automatic startup repair” loop. Would run diagnostics then stay on “attempting to repair your PC” indefinitely.Thought I could fix it myself so I booted into recovery mode and started trying some solutions I could find online.ran chkdsk - nothinran sfc /scannow - nothinFinally came across some solutions regarding my BCD. Without reading the fine print, I ranbcdbo

:)

 

Can't get GPU-Z to start with Windows 8.1 startup

I'm not sure how to do that. Could you list the steps for a noob?

 

WIN 10 Bluescreen Error at Startup

Hi,

Thank you for posting on Microsoft Community. I understand the inconvenience you are facing. I will certainly help you with this.

This error usually occurs if the Windows Boot Manager (Bootmgr) entry is not present in the Boot Configuration Data (BCD) store or the Boot\BCD file on is damaged or missing.

If this is a recently built new PC and you are unable to boot in normal mode, let’s try the following methods booting from an installation disc or USB and check if it helps.

Method 1:

I suggest you to try running Startup repair from Advance boot option. It may ask you to insert the Installation DVD/USB while doing startup repair. You have to create an installation media for that. You may download an ISO from the below link:

http://www.microsoft.com/en-us/software-download/windows10



(Refer to the section "Installing Windows 10 using the media creation tool " in the above article for creating the tool).

Once you have the installation media, follow the steps for Startup repair given in the below given link and check if it resolves the issue:

Windows Startup Settings:

Windows help & learning - Microsoft Support



Method 2:

You may try to rebuild the BCD booting from the disc and follow these instructions:

• Insert the installation DVD or USB and boot Windows 10 from it.
• In the ‘Windows setup’ page select the ‘language to install’, ‘Time and currency format’ and the ‘keyboard or input method’ and click on
  ‘next’.
• Click on Repair your computer.
• Click on Troubleshoot and then select Advanced Options.
• Click on Command prompt and type the following commands and press
  Enter after each command:

Bootrec /fixmbr

Bootrec /fixboot

Bootrec /rebuildbcd

• Restart the computer. Check if the issue persists.

Hope this information helps. Please post back with the results, we will be glad to assist you further.

Thank you.

 

How to clean up BCD entries? Rebuild the BCD?

This is normal that under Recovery Environment, The letters are re-assigned. This is why you have to be careful and select the correct one.
@dictum
Advice: Never use Easy BCD with Windows installed using GPT disk. Use Easy UEFI instead provided you know what you are doing. Easy BCD only works with MBR disk type.
Base on the screen shot above. Your disk 0 is your new Windows and your disk 1 contains the old Windows. Disk 3 contains a 512MB Fat32 partition and I don't know what that is. I suggest you disconnect disk 3 for now before proceeding.

Let rebuild new BCD's for both disk 0, and disk 1. Please follow step by step on the 2 screen shots below. On step 3, write down the drive letter for PM981_New. In the screen shot, My Windows is still assigned to C but it might be different from yours. In step 10, if the drive letter is different than C, then use the letter in step 3.

Do exactly the same for disk 1, this time select disk 1 in step 4 and assign letter V in step 7, Use V and the drive letter for Old Windows in step 10. This will create a new BCD for PM981_Old and you will be able to boot separately from boot menu.

From boot menu, select which one to boot from.
Once booted into Windows. If you wish, you can set up dual boot for Windows old & New. Under This PC, look for the drive letter of the offline Windows and type:
bcdboot X:\Windows where X is the letter of the offline Windows