If u wanna use a peltier, then u better do your homework first!
You have to work out the heat radiated from your cpu in watts and check that your peltier can absorb it (that depends on the voltage of your pelt).
Next you will have to power you pelt via a seperate psu. My 220w pelt should have ideally need something stupid like 40 amps! So what watt is your pelt? A 156w can be run of a 300w but you need to loop the 5V rail with a 1 ohm capacitor ( i think) to compensate for the 12v rail power load! Also if you use one psu, or the psu that has got no voltage load protection, the psu is liable to catch fire!!!
Then next thing (the most important) is cooling the hot side of the peltier. If you've got a pelt over 60 watt, then you'll need a watercool setup just to cool the hot side of the peltier.
Then if you manage to overcome all this, then you have to worry about water condensation. If you dont cover the cold side of the pelt which does not touch the cpu core, these areas will cool the air to ice which will melt into water.
So, yes you will mash it big time if you dont do it properly.
Apart from that, you'll have no probs.