Use the Command Prompt for startup repair from a Windows USB recovery drive

To use the Command Prompt for startup repair from a Windows USB recovery drive, you'll need to follow these steps:

1. Insert the USB Recovery Drive: Plug the USB recovery drive into your PC.
2. Boot from the USB Drive: Restart your PC and press the key that opens the boot-device selection menu for your computer, like the Esc/F10/F12 keys. Select the USB drive as your boot device.
3. Access Windows Recovery Environment (WinRE): Once the PC boots from the USB drive, you'll enter the Windows Recovery Environment. Choose your language and other preferences, then click on 'Next'.
4. Select 'Repair Your Computer': On the initial setup screen, look for and select the "Repair your computer" option which is usually found in the bottom-left corner of the screen.
5. Choose Troubleshoot: In the "Choose an option" screen, select "Troubleshoot".
6. Access Advanced Options: After selecting "Troubleshoot", click on "Advanced options".
7. Open Command Prompt: In the "Advanced options" menu, select "Command Prompt".

Once you're in the Command Prompt, you can perform a variety of tasks to repair your system. Some common commands used for troubleshooting and repairing startup issues include:

• bootrec.exe /fixmbr: This command repairs the Master Boot Record (MBR). It's useful if the problem is related to the MBR being corrupted.
• bootrec.exe /fixboot: This command writes a new boot sector to the system partition. It can be helpful if the boot sector has become corrupted or replaced with a non-standard Windows boot sector.
• bootrec.exe /ScanOs: This command scans all disks for installations that are compatible with Windows and displays the entries that are currently not in the BCD store.
• bootrec.exe /RebuildBcd: This command scans all disks for installations that are compatible with Windows and allows you to select the ones you want to add to the BCD store.

If you suspect your system files are corrupted, you can also use the sfc /scannow command which scans the integrity of all protected system files and repairs files with problems when possible.

After executing the necessary commands, type exit to leave the Command Prompt, then restart your computer to see if the startup issue has been resolved. If these steps do not resolve the issue, you might need to perform more advanced troubleshooting or consider other recovery options, such as restoring from a system restore point or performing a system reset/reinstall.