invalid arch-independant ELF magic

HI Ive bravely tried to install mint cin on an old windows laptop using a bootbale usb  i have changed the order in the boot menu so that the usb is first booted. however now im getting a black screen saying GRUB error : invalid arch-independant ELF magic

Ive looked online at various commands but all say 'unknown command'
Im still trying to get my head around linux .
i now have a laptop that doesnt work at all 

any help will be appreciated thanks in advance