Located on a small sticker on the bottom of the laptop or inside the battery compartment. For the PCG-31311L, this is usually VPCYB15KX , VPCYB25KX , or VPCYB35KX .
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Special keys (brightness, volume), VAIO-specific software, and touchpads may not work correctly. sony pcg31311l drivers
Since the official Sony support pages can be inconsistent or redirected, you have three main paths: Located on a small sticker on the bottom