You need the original Windows 10 installation DVD to repair the Master boot record.
If you don’t have the Windows 10 installation DVD to run Command Prompt, go to Fix MBR with Easy Recovery Essentials.
For more information go through the link: Mcafee Activate
The instructions are:
1.Boot from the original installation DVD (or the recovery USB)
2.At the Welcome screen, click Repair your computer
4.Choose Command Prompt
5.When the Command Prompt loads, type the following commands:
- bootrec /FixMbr
- bootrec /FixBoot
- bootrec /ScanOs
- bootrec /RebuildBcd
6.Press Enter after each command and wait for each operation to finish
7.Remove the DVD from the disk tray
10.Restart your computer and check if Windows 8/8.1 can now boot
If bootrec utility doesn’t fix your Windows 8/8.1, try following the next commands to fix the EFI bootloader of the Windows 8/8.1:
1.Boot from the installation DVD or the Windows 8 or Windows 8.1 recovery USB
2.Click Repair your computer
4.Choose Command Prompt
5.Type these commands in order and hit Enter after each:
- sel disk 0
- list vol
These commands will select the first disk of your computer and the list all the partitions available on that disk.
6.Check for the volume item that has the Fs column FAT32. The EFI partition must be formatted under FAT32.
If the volume number of EFI partition is “2”, type the following command:
sel vol 2. If the volume number is different than 2, replace “2” with the number available on your computer.
7.Assign a letter to this partition, a letter that is different that those already available on your computer, for example x:\.
8.Type this command to assign the letter:
9.Wait for the success message to appear:
DiskPart successfully assigned the drive letter or mount point.
10.Type exit to quit the DiskPart utility:
Type this command and replace x:\ with the letter you assigned earlier to the EFI partition:
cd /d x:\EFI\Microsoft\Boot\
11.Then type the bootrec command to repair the volume:
12.Now you need to backup the old BCD and recreate a new one. Type:
ren BCD BCD.backup
13.Type this command to recreate the BCD and replace the x:\ with the assigned letter earlier:
bcdboot c:\Windows /l en-us /s x: /f ALL
14.In above command, Windows is installed on c:\. If the drive letter where your Windows 8/8.1 is installed is different, replace c:\ with your drive letter.
15.Remove the DVD from the disk tray
17.Restart your computer