The laptop came with Windows 8 pre installed, with an option to upgrade to 8.1 which I did straight away if I recall correctly.
There is a Windows 8 sticker on the base of the laptop but I couldn't find a 25 digit code, only the model and serial numbers.
I tried tapping f10 on startup but unfortunately it didn't do anything and only proceeded to the same black screen as before. I have previously been accessing a menu (troubleshooting recovery, bios, boot from usb etc) using an assist button next to the power button. Is this a different function to tapping f10?