Hi,
On your keyboard is a key combination that sends the video display to your laptop's lcd panel or an external monitor. This may be what was changed or can be used to try and bring your display back.
You have a Fn key near the space bar. The writing on the Fn key is a unique color to the rest of your keytops. You use the Fn key plus another key to activate or deactivate certain special functions. One of the special functions is to send the display signal to an external monitor.
You can attach an external monitor to the blue socket on the back or side of your laptop and this may give you the display you need to reenter the system setup and change the instructions that your primary display is not external but the LCD panel.
Additionally, there is a keytop with the same color writing as the Fn key that changes your display from internal to external display. The icon used and or the acronym on the key varies greatly from manufacturer and series within the same manufacturer. Yours may be an icon, looks like the outline of a TV screen and may have a vertical line on either side. or it may use acronyms like lcd/crt where crt is a cathode ray tube, the common parlance for a TV like monitor and refers to an external display. Whatever letters are used or whatever icon is used, it should make visual sense when you see it. It will be in the same color as the Fn keytop. When you identify the key, you want to press the Fn key and the special key at exactly the same time. To do this and get your display back, you will need to first start your laptop. Then, while it is running, press the Fn key and the special key.
Let me know how you make out, especially if this works so I can give you some more information to go on as a VAIO user.
Regards,
Worldvet