Hi Alihyde75,
Welcome to Sony Community!
I understand that you want to reformat the unit to factory setting, if F10 doesn't give you an option to do it then it's possible that the hidden partition is not there anymore. We suggest getting a VAIO recovery disc to reinstall all the drivers and software that came with the unit.
We highly recommend visiting our Sony Global Web site for information on contacting the Sony Support Center in your region at http://www.sony.net/SonyInfo/Support/ to assist you with this issue.
Regards,
Jen
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