http://blog.lenovo.com/en/blog/how-to-enter-the-bios-setup-utility-or-boot-menu-with-windows-8-1/

By default, a Windows 8/8.1 shutdown is not a real shutdown. Instead, it is hybrid shutdown where contents of memory are saved to disk. This allows for a faster startup. However, turning on the PC after a hybrid shutdown does not allow for pressing F1 or F12 during startup.

There are several ways to enter Setup Utility (F1) or the Boot Menu (F12) on a Microsoft Windows 8/8.1 PC as explained below:

1. Press and hold the Shift key while selecting the Shutdown option in Windows 8. This will make the PC perform a full shutdown instead of a hybrid shutdown. Then F1 or F12 can be pressed successfully during startup.
2. Select Restart instead of Shutdown. Then F1 or F12 can be pressed successfully during startup.
3. Disable the fast startup option in Control Panel -> Hardware and Sound -> Power Options -> Choose what the power buttons do.

It is also possible to access these features from within Windows 8/8.1.

To enter Setup Utility:

1. Open the Charms Bar by pressing Windows Key-C or by swiping in from the right edge of your screen
2. Click on Settings
3. Click on Change PC Settings
4. Click on General
5. Scroll to the bottom and click on Advanced Startup, then Restart Now
6. Click on Troubleshoot
7. Click on Advanced Options
8. Click on UEFI Firmware Settings
9. Click on Restart

To access the Boot Menu:

1. Open the Charms Bar by pressing Windows Key-C or by swiping in from the right edge of your screen
2. Click on Settings
3. Click on Change PC Settings
4. Click on General
5. Scroll to the bottom and click on Advanced Startup, then Restart Now
6. Click on Use A Device
7. Click on Boot Menu