Hello everybody, this is my 1st ever post on PPRuNe, so please be gentle with me - despite lurking for a while...
I must admit it does possibly look like a heat problem (unless you have already let it fully cool down for a few hours and it is still present), as if it is visible while loading the BIOS, the Windows drivers are not yet loaded so can therefore be discounted. As others have said make sure there is no obstructions that prevent air circulating
You can also try removing the mains adaptor and battery, and then press and hold the power button down for a few secs to dischage the motherboard/gpu (your BIOS settings will remain intact), and see how you go on from there.
Good Luck !