efi problem

["mick.crane" <mick.crane@gmail.com>]

I suspect the GPU is suspect because there are small blocks of pixels 
appearing where they aren't wanted.
I'd like to re-install the OS as I've got copies of everything I think.
Just to see if it's maybe a driver issue.
Thing is I can't get the f12 options screen of the PC to let me boot 
from a CD in this EFI mode what's grub done.
How can I boot from CD in this EFI mode?

mick