If an upgrade pack has been installed on a VAIO computer with Windows 8 preinstalled, such as the Windows 8 Media Player or Windows 8 Pro version upgrade packs, and the operating system is reset, you will be prompted to enter the product key for the upgrade pack. If a complete system recovery is performed, the computer will be returned to the original factory condition and you will need the product key and install media in order to reinstall any upgrade pack.
If you purchased software or operating system upgrades using a retail channel, the Key Card that came with the product will contain the appropriate product key. If you purchased and downloaded software from Microsoft using the Add Features option, the product key can be found in the original email sent to you from Microsoft after purchase.
IMPORTANT: If the product key has been lost or forgotten, you will need to contact Microsoft at 1-800-Microsoft for the appropriate product key. Sony does not have product key information to provide. This is not a Sony decision, rather a restriction imposed by Microsoft.