|All I can do is inside windows, no F keys at start up.|
Maybe I haven't described the situation properly.
The laptop's screen panel is broken.
The external monitor is permanently connected to the laptop and I have set it as default monitor.
When I press the power button, to open the laptop, I don't see the start up screen, some seconds later, the external monitor opens and I see the windows login screen.
There's no point in entering BIOS or whatever because I don't see any of these.