No I have not overclocked the cpu. The cpu model is Intel® Pentium® Processor Extreme Edition 965 (4M Cache, 3.73 GHz, 1066 MHz FSB). The normal clock speed for the processor is 3.73GHz. The aftermarket cooler is Cooler Master Hyper N520
Do you have thermalpaste on it? Although even if you didn't idle CPU temp should not be 70c.
I would say replace that heatsink with the stock first see what happens. Do you have a rear fan as well? Because typically when you have a heatsink like that where it uses a flat fan that faces the exhaust, having a rear fan in addition will cause countercurrents. I remember buying something similar for my core 2 duo thinking it would be better than the stockfan. Not only wasn't it better, but my idle temps went from 32c to 45c. So scrapped it and bought thermaltake's cpu fan and now I have idles of 30c.
Don't be too concerned about GPU. They run that hot idle since the fans mainly disabled. My 9600 gt idle without fan is around 55c, with 100% fan manual setting its 50c idle, with manufactuer saying it can get as hot as 90c on full load.