I was handling my CPU cooler after taking it out of the box and accidently smudged it with my thumb. You can see a good bit of the copper underneath, but after researching a bit I found that it should spread evenly after being heated up. I'm wondering if it's still okay to install as is, even though there's nearly a fingerprint size smudge taking up about a quarter of the thermal paste. For the record, this is the processor I have, it has the square of thermal paste pre-applied: http://www.(competitor)/Product/Product.aspx?Item=N82E16819103849
Use alcohol swabs to clean off the thermal paste residue. Then apply a thin, even coat of Arctic Silver 5 thermal compound. Wrap your finger in a small piece of plastic and spread the compound around. Remember, thin, as even as possible.