Got a fix for you here.
Hit start, then type in regedit and hit enter. Accept the UAC prompt, and once the Registry Editor opens, open each of these in order:
From here, look for the value on the right with the name TypingInhibit. Double-click it, and change the 0 to a 1.
This does the same thing as what selecting the checkbox would do, only without having to make the checkbox appear.