I bought an used VAIO MODEL pcg61a11u and after formating it's HDD with another pc I'm prompted with a "operating system not found" screen. I feel that the original owner changed the BIOS to legacy but I cant acces the BIOS anymore since the assist function no longer exists. what can I do? should I try to install windows in legacy? I'm not sure how to do that, please help I really need this to work.