Missing os and reboot and select your boot device

[Rajmohan_1]

Please help me when I get into the booting it shows the error as
Missing Operating system

reboot and select your bootable device like that

 

[Colif]

on another PC, download the Windows 10 media creation tool and use it to make a win 10 installer on USB or DVD

change boot order so USB or DVD is first, hdd second
boot from installer
on screen after language choices, choose repair this pc, not install
choose troubleshoot
choose advanced
choose command prompt
do the following and restart PC afterwards should allow you to boot.

It is important to note that changing Active Partition wrongly may make your computer unbootable. So do not by mistake, mark a partition as Active, if it does not contain the NTDLR loader for your operating system.

To do this, enter the following commands (in bold):
diskpart
list disk

Now select the disk – it will typically be Disk 0 – and set it as the Active disk. Assuming it is Disk 0, the commands become:

select disk 0
Now list the partitions using:

list partition
Assuming your partition number is 0, the command becomes

select partition 0
To make it the Active partition, type the following and hit Enter:

active
Exit diskpart.

http://www.thewindowsclub.com/the-drive-where-windows-is-installed-is-locked