Windows 8 starts really fast. It seems that one of the reasons is that it skips the old settings which checks the hardware. This means that you cannot use the old BIOs settings to change the boot unit, for example.
If you want to switch back to the old BIOs menu, do the follow
1. Move the mouse to the top right corner to activate the corner menu.
2. Click on Settings.
3. Click on "Change the settings of the PC"
4. On the new menu, click on "General Use"
5. At the bottom of the menu, under "Advanced restart", click on "Restart now".
6. It will shows you different options. Click on "SetUp" to go to the BIOs Setup menu.
Optionally if you want to use the boot menu, do the follow.
1. In the BIOs menu, select Boot
2. Disable the "Secure Boot"
3. in the "Boot List Options", select legacy
4. Go to Exit menu and select "Exit Saving Changes".
Be aware that if you change this, you cannot switch back to the Windows 8. If you want to use Windows 8, you must Enable the Secure Boot and select the previous Boot List options.