Repairing Windows Boot / Startup Process

Here is a collection of fixes to fix a broken boot sector and get Windows 10 starting up again as original.

A:

Get into your Windows recovery terminal, by booting with the installation disk, then enter:

1. bootrec /fixMBR

2. bootrec /fixBoot

3. bootrec /rebuildBCD

4. Enter ‘A’, press ‘enter’
This is the step for the worst-case scenario, when the system will not even boot to safe mode.

B:

In an administrator command prompt, after booting into safe mode with networking:

1. DISM.exe /Online /Cleanup-Image /RestoreHealth

2. sfc /scannow

3. Attempt Windows Update and/or Restart
Step 1 can take over an hour but should not take more than 24, it depends on your connection. Step 2 is similarly timed but does not require internet access.

https://technet.microsoft.com/en-us/library/hh824869.aspx

As an additional measure:

If you have a single system reserved partition with a system status make sure it is ‘Active’ in disk management.

If you have more than one, be careful. No tips for that here, look for the ‘system’ status. If you have no system reserved partitions, leave it alone.

If you’re in disk management and you can boot Windows under some (if not all) conditions, stick to tips A and B.


Check:
http://www.tomshardware.com/forum/id-3145032/windows-boot-failure.html