Letís try these steps and check if it helps.
1. Boot up from your Windows 8 disc.
2. Don't click 'Install Now', click Repair Your Computer.
3. Click Advanced Options.
4. Click Other Options.
5. Click Diagnose my PC.
6. Wait for your computer to reboot.
Your computer has now an unlocked hard drive.
You may also refer to the link and check if it helps.
: Modifying BIOS/complementary metal oxide semiconductor (CMOS) settings incorrectly can cause serious problems that may prevent your computer from booting properly. Microsoft cannot guarantee that any problems resulting from the configuring of BIOS/CMOS settings can be solved. Modifications of the settings are at your own risk.
Hope it helps.