Vaio Z5 - graphics disappeared

My apologies if there's topics on this already, I've tried searching for a while but I'm possibly not used the right search terms or the answers are buried in owner's threads so would appreciate some advice.

I have a Vaio Z5 bought late last year which came with W7, today I was fiddling around with a new boot tool (A version of WinPE built using MDOP) which I tested on the Vaio. It didn't work as the tool couldn't see the hard drive as I hadn't loaded any sata drivers so I left it and went back to W7. However despite not touching the hard drive, the Z5 has gone steadily wrong since then. The switch for the integrated and discrete graphics card no longer lights up for either option and switching it over seems to make no difference. The first problem was the system claimed it couldn't find any Intel graphics drivers, I tried booting again on the Speed mode and this time it found drives and put a system tray icon in despite being on the Nvidia setting. On the next boot with the switch set to Stamina it claimed it couldn't find any drivers and changing the switch seems to make no difference, no drivers for Intel and the Nvidia card disabled.

The problem I'm having is I don't actually know how the switchable graphics work so I'm not sure where to start troubleshooting, it obviously doesn't use hardware profiles as those appear to be gone in Vista onwards. Does any of this sound like a known issue or has something bizarre gone wrong with the machine? There's not that much on it so if it is a strange one I'm fine with just restoring it back to its shipping state for convenience as this is my machine machine.

Edit: I should note everything else looks ok in device manager although the power management doesn't appear to be working normally, when I switch from power save to high performance and back again it doesn't change the backlight settings as it previously did.

Edit2: Looks like it may be fixed, I've never seen System Restore work so rarely bother with it however I thought I may as well give it a shot and I'm impressed to say it seems to have fixed the problem, the switch now lights up again and the machine appears to be loading the drivers properly for each graphics card. Hopefully it is fixed although still a bit baffled as to what went wrong, something else I noticed was that the clock had jumped forward about 6 hours onto the next day, still the same time zone though

Thanks for any help,
John