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#1
Have you tried the troubleshooter in control panel?
Here's what I found on that error code,
Error Code 80070BC9 and 800B0100 in Windows Update
1.Reregister WU components in aggressive mode How do I reset Windows Update components?
you can also try reregister all WU modules Repair & Fix Windows Updates with Fix WU Utility | The Windows Club
2.Open regedit,and make sure you have this key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\RebootRequired
if you have it then delete this key +restart
I reinstalled the OS because when I once shutted it down it corrupted Windows 7 and I can't repair it. It is working now.