Just to expand on the correct steps mdh347 provided, here are the steps with some images:
With the computer turned completely off, press and hold the Assistbutton until the black VAIO screen appears.
NOTE: The location of the Assist button will be different depending on the computer model. Refer to the operating instructions supplied with the computer for the exact location of the Assist button on your model. Manuals are available online through the Manuals/Specs/Warranty link on this page.
At the VAIOCare | Rescue Mode screen, press the Down Arrow key until the Start BIOS setup [F2] option is highlighted, and then press the Enterkey.
In the [BIOS Name] Setup Utility screen, use the Arrow keys to navigate through the various setup screens and options, use the Enter key to select different screens and options, and use the ESC key to exit the different screens or options.
NOTE: To reset the computer BIOS to the original default values, press the F9 key and then save the changes and exit.