Error: Failure configuring Windows updates. Reverting changes. Do not turn off your computer when you try to install Windows Updates
http://support.microsoft.com/kb/949358
or
Perform SFC scan to check if there is any system corrupted files.
Use the System File Checker tool to repair missing or corrupted system files
http://support.microsoft.com/kb/929833/en-us
or
Fix Windows corruption errors by using the DISM or System Update Readiness tool
http://support.microsoft.com/kb/947821/en-us
or
“Restore your PC to an earlier point in time”:
http://windows.microsoft.com/en-US/windows-8/restore-refresh-reset-pc
also see:
http://support.microsoft.com/kb/949358/en-us (Perform a System Restore)
or
Perform System restore from the Windows recovery and check.
a) After you boot your computer using Windows DVD or System Repair Disc, a black screen appears with gray text "Press any key to boot from CD or DVD". Press any key.
b) Select the correct time and Keyboard type.
c) Click Repair your computer in the lower left corner.
d) Select Troubleshoot from Choose an option screen.
e) Click advanced options in Troubleshoot screen.
f) Select System restore.
Important: System Restore will not revert any of the non-system files like documents, email, music, etc. to a previous state. These types files are completely unaffected by System Restore. If your intention with this tool was to recover
a deleted non-system file, try using a file recovery program instead of System Restore.
Reference link:
How to refresh, reset, or restore your PC.
http://windows.microsoft.com/en-IN/windows-8/restore-refresh-reset-pc
If you do not have Windows installation disc or System Repair Disc, contact the computer manufacturer.
You can also refer to:
How to create installation media for a PC refresh or reset:
http://windows.microsoft.com/en-us/windows-8/create-reset-refresh-media
Upgrading Windows with only a product key.
http://windows.microsoft.com/en-us/windows-8/upgrade-product-key-only