How to change the default delay on the boot menu from 30 seconds to 5 seconds on windows 8
I suspect that you may be talking about the delay during the "Select an operating system" screen during boot, that defaults to 30 seconds.
To change this:
open the System control panel (shortcut: Windows+Break)
select Advanced System Settings from the left hand menu:
Click the Settings button in the Start-up and Recovery group:
Edit the Time to display list of operating systems to suit: