Please do the following checks..
The Power off and on the Laptop again..
Are any of the keys stuck down?Does it do this when you reboot the machine e.g. can you press F2 or Del to go into setup?Also are you familiar with the 2nd function keys on the laptop (usually defined in blue on the key) to access these you usually press a "Fn" button to activate the blue part. Maybe you activated a keyboard lock by accident. If you have the manual maybe check this or call dell on http://www.dell.com/ and use the online tech support.
I hope the information helps and expecting your acceptance..