I don't do much old work, so this may sound basic to guys that do this all the time, but:
I have a customer that has a few receptacles with no ground in the box. The wire is in great shape, but for some reason, the installer cut off the ground wires back to the sheath of the romex, leaving me with nothing! Argh!

What is the correct way to treat these? I am thinking a GFI w/o a ground will be the safest thing I can do for them. If I put one at the beginning of a run, will it protect all the outlets downstream in this configuration? I would like to run new wire to each, but that may not be possible on a few of them.

Thanks for any help,
Mike