Check this page: Sony eSupport - Windows 10 Upgrade information
"Important: Although Microsoft is already offering the Windows 10 upgrade, it is strongly recommended that you wait to install it until the drivers & installation instructions are available for your VAIO PC model."
I would like to advise you that the driver support for the first generation of Intel® Core™ Processors with Intel® HD Graphics is not available at the moment.
To verify this, please feel free to visit: Supported Operating Systems for Graphics Drivers
I know the first gen is not included in the list but the 2nd is, with that we can know the first gen is not supporting Windows 10* regarding graphics drivers.
If any further information or support is required, feel free to contact us back.