troubleshooting

In a similar situation, I was able to correct it by resetting CMOS by removing the internal system battery for a couple of minutes.

Unfortunately, accessing the internal battery on most laptops can be very difficult since many times, it is located beneath the keyboard.
[b]Use extreme caution when dismantling your laptop and follow the service manual from the manufacturer closely![/b]
If you do not have experience with this procedure, it is best to take the laptop in to an authorized service center.

1. Do either the built-in or USB work before Windows loads? I.E. Can you access the bios settings. It could be something as simple as getting into the bios (usually done by pressing F10 or Delete before the Windows loading screen starts) and turning on USB keyboard.

2. The built-in keyboard may have a loose connection. Most times, on Sony laptops you can remove the keyboard without having to do major surgery. Turn it over and remove the screws that have a picture of a keyboard next to them. Once the screws are removed, turn it back over and lift the screen. Now, you should notice a couple of tabs on the top of the keyboard that slide underneath the plate that has the power button, etc. on it. Slide those tabs down and the keyboard should lift right out...there will be two cables connecting the keyboard to the system board...check these to make sure they are connected firmly.

3. Finally, are there any PS/2 adapters for a keyboard on the machine? They are the old round purple plugs that look like an S-Video connection http://en.wikipedia.org/wiki/PS/2_connector. If neither of the previous solutions work, you might try using a PS/2 keyboard or purchasing a PS/2 plug adapter that turns the USB keyboard into PS/2. TigerDirect