This is why reading is important. Any reading at all on the subject of mining would reveal that unless you are using equipment specifically made to mine bitcoins you are wasting your time. The time for mining with your PC is gone.
Not really.
The time to buy a bunch of GPUs just to mine bitcoins is rapidly closing if it isn't already gone.
The time to throw your othersise idle gaming rig on to mine a few dollars is still here but probably disappearing after a few runs of the BFL miners ship unless you don't pay your electric bill (utilities-included apartments, you electric heat almost year-round, etc).
I made around $20/mo worth of BTC at current prices on my old GPU and it doesn't cost me anything but a bit of time setting the miners up to autorun at low priority. My computer would otherwise be idle and I don't pay the electric bill here. if I paid electric then I probably wouldn't do it for $10/mo.
Go in with reasonable expectations of what you get for having your computer do a marginal amount of work and you'll probably be OK.