I have the following kit :

PS : Seasonic S12 500 Watt
MB : ASUS P5K-E WiFi (01/03/2008 BIOS)
CPU : E7200 @ 2.53 / 266 (not sure what batch)
Cooling : Thermalrigjt HR-01 Plus + Sycthe 1200 RPM
MEM : Corasir DDR2 8500 1066

Many people seem to be getting decent overclocks but for whatever reason I cannot seem to get this thing Prime 95 Stable @ 3.5 Gig or more. It will post at 3.8 / 400 but Prime 95 fails straight away.

I've tried :

1) Upping all the voltages one at a time to the "Safe Max". Taking notes as I go.

Vcc = 1.4
FSB Termination= = 1.4
NB = 1.7
SB = 1.55

2) Disabling PCIE / CPU Spread Spectrum / Transaction Booster

3) Manually setting PCIE to 100

4) Dropping the memory down completely so it shouldn't be an issue

5) Full Load Temps are OK @ 55/56 with 1.36 Volts (Voltage drops a little under load but that's normal apparently)

6) +5V line seems stable at 4.94 and drops to 4.92 under full load but doesn't budge from there

If anyone has any ideas or advice with overclocking on the ASUS P35 MB it would be greatly appreciated. Perhaps I just don't have a good overclocking CPU.

Its all about the Vcore. You might have a huge V-droop. Also I'd update that bios asap. Was the e7200 even around in January, I think it came out in March. It might not be fully supported by your Bios.

Some times it helps to change the multiplier lower. Give it a shot.