so here is my problem so i bought this macbook from 2008 completly got rid of the osx on it and installed windows and now no matter what i do i cannot boot from the usb im trying to install lakka which is a retro all in one emulator but no matter what i do i cant get it to boot of the usb. what happens is i hear the chime then a grey screen then windows starts up i cant acsees the bios or anything please help