Just bought Acer laptop (series 5517) and the

DOES THE MOUSE WORK OK?
If not, re-boot and press the [F8] key to get into the "Safe Mode" screen. See if the keyboard works in Safe Mode.
If so, go tothe Control Panel and select "keyboard" and update the drivers.
If not, then re-boot and select the [F8} key again, but choose "Start computer in last known good configuration"
If it still doesn't work, but the mouse does, then the keyboard is disconnected or the connector is loose; open 'er up and connect it.

I am not sure what is going on but try to press and hold the Fn key + the Number Lock key.