Method 1: Boot from the Windows 8 installation media and then perform automatic repair and check if it helps.
Follow the steps to perform system restore:

 a.     Insert installation media and restart the computer.

b.     Select language and click on Next.

c.      Select Repair your Computer and click on Skip this drive.

d.     Select Troubleshoot and click on Advanced Options.

e.     Here choose the option Automatic Repair and follow the prompted instructions.

 
Method 2: Use the Bootrec.exe tool in the Windows Recovery Environment to troubleshoot and repair startup issues in Windows
 Follow the steps to open command prompt using Windows 8 installation media:

 a. Insert installation media and restart the computer.

b. Select language and click on Next.

c. Select Repair your Computer and click on Skip this drive.

d. Select Troubleshoot and click on Advanced Options.

e. Here choose the option Command Prompt and type:

     bcdedit /export C:\BCD_Backup

     c:

     cd boot

     attrib bcd -s -h -r

     ren c:\boot\bcd bcd.old

     bootrec /RebuildBcd

f. Instead of /RebuildBcd, you can also try these options:

        a. /FixMbr

       b. /FixBoot

       c. /FixBoot

       d. /RebuildBcd