[ubuntu] Changed permission and bricked my computer, can't even reboot

view story

http://ubuntuforums.org – I was trying to install a copy of windows 7 on another hard drive using an iso and mounting it as a bootable flash. When I mounted the iso to the flash drive it gave a warning that the flash drive was read only. Using my VAST (not really...) knowledge of ubuntu, I opened that folder in terminal and typed in something along the lines of sudo chmod 754 / assuming that I would be pointing to my current directory. (might not have been exactly this, but the issue remains that my permissions are royally screwed up. It immediately exited me out of my browser and changes all image icons to ei (Hardware)