You may try to rebuild the BCD (Boot Configuration Data) booting from the disc and and if still issue persists better to go for fresh OS installation.
Follow below instructions to rebuild the BCD booting from the disc:
a. Insert the installation DVD or USB and boot Windows 8 from it.
b. In the ‘Windows setup’ page select the ‘language to install’, 'Time and currency format’ and the ‘keyboard or input method’ and click on ‘next’.
c. Click on Repair your computer.
d. Click on Troubleshoot and then select Advanced Options.
e. Click on Command prompt and type the following commands and press Enter after each command:
Bootrec /fixmbr
Bootrec /fixboot
Bootrec /rebuildbcd
f. Restart the computer. Check if the issue persists.
