Hi Alex,
Thank you for posting your query in Microsoft Community forums.
I understand that you need to know how to keep numeric keypad "On" during start up of Windows 8.
Are you referring to the Numpad or On-screen keyboard.
By default the numeric keypad status is the same as it was in when you properly shut down the computer. If it was on when you shut it down it will be on when you again turn the computer on.
If you wish to change the start up features, please contact your system manufacturer to change the bios settings.
Note: 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.
If you have any further queries or any queries related to Windows, feel free to post. We will be glad to assist you.