I have an old Toshiba Equium laptop running Windows 7. It’s runs fine and does what I need it to do however it has developed an irritating fault. On start up, the screen doesn’t always spring to life. There is no rhyme or reason to this at all, it can be working and I can power down and immediately restart then sometimes it’s works and sometimes it doesn’t. I know it’s not the motherboard as if I connect to an external monitor this works every time. I’ve tried removing the battery and draining residual power but still not different? Any ideas?