Vostro 5620 screen rotated by 90 degree at POST

Hi there,

I have got a Vostro 5620 where the display is rotated by 90 degree at POST screen. Once Windows is loaded, the display is normal again.

This is before Windows is booted up so the Ctrl+Alt+Up and Display Properties options are not available.  

Is there some other key combination that could rotate the screen back please?

Thanks.