@@somebody_thathe means the black starting windows screen with the animated windows logo I have the same problem but I've turned off secure boot and have the same problem
My neighbour gave my little brother a laptop and installed win10 first it didnt work good lagged so much reinstalled it to 8.1(absolute shit he says) and said the laptop cant run windows 7 , but how did it run 8.1 and 10 then? never reinstalled windows before,should i try to reinstall it for my bro on his laptop?
you need to dualboot if you want 2 windows versions but its risky to do it, you cant recovery old files if you format all your impronant files and install windows 7 in main hard disk.
if you have nvme or gaming new hard disks then thats the problem, microsoft dont support windows 7 anymore please use old hard disk to install windows 7