Can I change the root drive?

I'm having trouble booting off my hard disk. I can boot off a flash drive then mount the hard disk and use it without trouble, but the directories are all off. Is there a way to remount, say /disk to / ? mount -o remount would seem to do this, but doesn't, possibly because / is already in use. I can execute individual commands with chroot, but the libraries are in the wrong place.