How Do I Unlock The Keyboard On A Gateway Notebook?

In fact you've made the setting in BIOS setup in such a way that your keyboard get locked. You need to change the settings again to the default settings. You can go to these settings by restarting your notebook and then immediately press "F2" button.

I have a Gateway LT M1625. On it you hold the function key on the bottom left and press the Scroll lock key at the top just to the right of the F12 key.