Keyboard Fn + Fxx keys do not require a driver. If those keys aren't working the keyboard is faulty.
This is wrong. Some laptops don't require drivers as they are done through firmware, but some laptops do require them as they are done using filter drivers in combination with software to work.
To OP, go to esupport.sony.com and click on the drivers link. Find your model number in there (the number you provided isn't exactly listed. Look for a different but similar model number on the bottom of the PC), and download the VAIO update software. Then run that software, it should download everything you need.