Access boot menu from Windows 8 PC

Solution 1:

While running Windows, hold Shift as you click on Restart under Power in the Settings charm to access the boot menu once you restart your computer. From this boot menu, you can enter the UEFI firmware setup utility. More information.

Windows 8 will automatically start the Startup Repair Tool if it detects it cannot boot after two consecutive attempts, and will open the boot menu if it detects that the system has restarted twice in quick succession (in order to handle situations where the boot sequence completes, but the system remains unusable).

Solution 2:

Just change the boot type to Legacy. Worked for me and you won't have to go through Windows. I know it's a late information, but might be useful for others.