How to enable Legasy on a laptop with UEFI?

Question

linux

HP Pavilion G6 laptop ..
there was a Win8 + Ubuntu 16.04 dual boot ..
at one fine moment when you turn on the laptop, a black screen, the fan spins and that's it ..
I pulled out the battery, reset the BIOS to default ..
after that I could only run Ubuntu in "recovery mode" ..
the laptop categorically ceased to recognize bootable flash drives, nevertheless, the flash drive with Win 8.1 went with a bang and everything was installed, except for the firewood on the video cards (there are two of them in the laptop ..).
As far as I understand, in order to boot from the flash drive, you need disable Secure boot and enable Legasy ..
but when I turn on Legasy, I am met with a black screen and nothing but resetting Bios settings does not remove it ..
Question: how to cure this ?? .. is this a problem with hardware or software ?? ..
PS: Logically, it would be necessary to change UEFI, but I did not find intelligible manuals about this ..

Answer 1

No, that's wrong, Legacy should not be included. Otherwise, then UEFI "cannot".

Answer 2

uh ..
though a little late, but still ...
in short, the problem turned out to be in a flying discrete video card ..
after the chip was soldered - everything came to life, ran, switched over ..))
I think that when the secure boot is turned off, the built-in the video card is not recognized in the processor, but I xs .. I can be wrong ...
Happy New Year, comrades !! .. )))