While the E7200 might be binned lower than E8000's, I'd be surprised if all these bad o/c's were due to crummy cpu's.
I find the most common roadblock to o/c, is the ram...or trying to run the ram at too tight of timings (4-4-4) with too low of voltage. Even if the ram is rated 4-4-4, I would set timings to 5-6-6-18 with 2.1v while testing. This should remove the ram as a o/c'ing roadblock, then you can concentrate on increasing the FSB and cpu voltage.
According to Intel documentation, the maximum recommended voltage for the Wolfdales is 1.3625v. Any voltage above that can lead to cpu degradation and shortened life. The maximum recommended FSB Termination (VTT) is 1.115v. 1.2v is overvolted, although some motherboards only go that low.
Most of the bios settings have little effect on successful o/c's to 4.0GHz or even 4.2GHz...other than, cpu voltage: 1.3625v max; ram voltage: 2.2v max (but I run mine at 2.0v and would not go above 2.1v); and depending on your m/b, the Northbridge voltage could be increased to 1.4v or even 1.55v for stability. You could also kick up the Southbridge voltage a notch if it suits your fancy. I enable Load Line Calibration (cpu voltage damper) to reduce vdrop and use the NB .61x ratio. I would keep most the remaining bios options in their default settings.
One trick to speed up your computer is to enable "Transaction Booster, or Performance Level", which at the "2" setting improves my memory latency by 30% (Performance Level 6 rather than the stock 12). Also changing to the 400MHz bootstrap improves my ram latency nearly 5% over 333 bootstrap at the same frequency.
