Hi, Owais_1128,
Thank you for considering Sony Community!
If your Sony Vaio came with Windows 8 or 8.1, the product key is already embedded on its the motherboard. No need to enter it after reinstalling the OS (formatting using the recovery disc). Older models usually came with Windows 7, Vista and XP, the product key is located on the bottom of the unit, usually on a white sticker.
For further assistance regarding your concern, please contact the Sony offices/Sony representative offices nearest to your place of residence in Asia Pacific region http://www.sony-asia.com/countryselector.html?hpid=countryselector:AsiaPacific. Due to proximity, they are in a better position to respond to your questions or concerns.
Regards,
Vincent
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