Q6600 hp computer problems

Hi, I am new but have a few technical questions regarding my hp computer. I recently got it with a q6600 -b3 , but anyways when i open cpu-z and look at the clockspeed it is around 1.6 ghz. Is this because of the speedstepping thing where it shuts off the other 2 cores when an application isnt in use or is my computer really being underclocked by hp .8 Ghz? Secondly, Is the hps powersupply too small to even try to OC my computer on air? I think it is going to run hot even after installing my EVGA 7600 gt because I heard the power supply is only like 350W? I think i may upgrade to around 700W or so in the future tho. Also, what exactly is a driver- is it like just programs to make things run smoother with the BIOS? Lastly, how do you overclock a computer lol? Is there a program where u can change the multiplyer and voltage and what not or do you just keep cooling it and hope it OC itself? I know this sounds newby but is there a simple definition for these questions? Thanks, Russell.