If you just want to try it for fun just get a few USB miners or cheap ASIC. Not that I suggest it, but as an example I bought a block erupter cube for $2 recently, which is substantially more powerful than your setup. $.10 per kW/h is way more than what I pay and I still won't run things that inefficient unless I'm using it for a space heater, but it would still be better electricity spent than running the computer for the hash rate.