question of old wiring/ungrounded outlets

I'm living in an older house (original house was likely built in the 1930s) that has had several renovations through the years. the wiring was likely brought up to code in the late 50's - early 60's, including the use of a circuit breaker box. Only one thing: none of the outlets in the older portion of the house were grounded. I've noticed by looking in the box that there is a double pole 20 amp switch that feeds some of the outlets (unsure what else, if anything). My question is: would it be possible to use one of the 3 wires as a ground, and switch out the double pole for a single?