Some of the keys on my laptop (Sony Vaio VGNFSF810W) stopped functioning. So I bought a replacement keyboard from Sony and installed but the problem remains. Is there something else I can look into to find out what is creating the problem?
I have seen this far too many times. This is usually due to the pins on the connector (between keyboard and motherboard) failing.
The only way you can get it repaired is for them to acknowledge a fault / or a replacement whilst still in warranty, or find a replacement motherboard/a company that can do board level replacements.
You may also have luck rubbing /cleaning the pins to increase contact... or even if it is only the end tips that are worn, if you only stick it in half way, but use tape to make sure it is secure, you may be able to make a connection further down.
First things first, you need to rule out the operating system. I assume you're using Windows? In which case, try booting up in Safe Mode with Command Prompt.
Press F8 just before the Loading Windows screen appears - it should give you a list of boot options - one of which should be something along the lines of Safe mode with command prompt - the actual wording varies in different versions of windows.
Once the command prompt has appeared you can try out the keyboard to see if it's working OK.
If it is then the problem is most likely either a driver or keymap localization problem and you should check out the settings within Windows.
If it is still playing up then the problem may well be with the motherboard, and repairing it will be costly.
Plug in a USB keyboard to see if that works correctly. If it does then it may well be the motherboard.