Sorry John, I have been away for a few days.
It is possible to install a Windows 10 nVidia driver but it will not install unless the installer is modified. Only drivers signed by Sony will install without modifying the .INF file and, understandably, Sony do not recommend what is a bit of a hack. However, as this is the only way to update, many try this way forward. You will have to Google for information on this and it will be at your own risk. By installing a single nVidia driver means that the on the fly switching from 'speed' to 'stamina' will be lost.
Most users of Z-Series Vaios continue to run Windows 7 as recommended by Sony - especially as it is not a touch screen laptop. The problem with this is that drivers such as the graphics driver are now very old and may not support some of the latest games. However, the size of the Z-Series is not conducive to gameplay and the drivers are OK for most other purposes but you may still run into problems with some newer graphics applications from providers like Adobe.
The choice is yours. Reinstalling Windows 7 Pro will be far easier if you have a set of original Recovery Discs which will reinstall all software, divers and utilities as well as Windows 7. If you do not have these discs, you will need to download all the original drivers from the Sony website. BUT some software is not available for download and only available on Recovery Media but as you don't have this now, it is unlikely you will miss it.
Good Luck!
