How do I fix Windows 10 OS not found?

Method 1. Fix MBR/DBR/BCD

1. Boot up the PC that is having an Operating system not found error and then insert the DVD/USB.
2. Then press any key to boot from the external drive.
3. When Windows Setup shows up, set keyboard, language, and other required settings, and press Next.
4. Then select Repair your PC.

19 июн. 2018 г.

How do I restore my operating system?

To restore the operating system to an earlier point in time, follow these steps:

1. Click Start. …
2. In the System Restore dialog box, click Choose a different restore point, and then click Next.
3. In the list of restore points, click a restore point that was created before you began to experience the issue, and then click Next.