This can have a number of causes. The most likely cause is that the keyboard is either plugged in incorrectly, or an input device has been enabled which takes priority over the keyboard so it cannot be used by default. In Windows, there are two processes that will give other devices priority overuse of the Keyboard – one is the Mouse and Touchpad functionality (available by pressing F8 during bootup), and another one is BitLocker (which protects data on your hard drive and programs from prying eyes). If you would like to disable these features then please consult the instructions below:
To disable Mouse and Touchpad functionality: Hold down the SHIFT key as soon as Windows boots up.