[ccperf721p]

The P5E has a glitch when trying to use the 4:5 divider when overclocking, not sure what FSB you are running when trying to set ddr2-800 for memory speed so I can't say for sure if you are running into this.

The board also has some pretty significant voltage drop under load (there are some easy methods of modding this though).
Another thing I noticed with these boards is if you happened to move or bump the heatsinks while installing the board or components it's a good idea to remove the board, and use some Ceramique on the factory cooling arrangement.

Disable C1E , CPUTm, and Speedstep under CPU Config

Set the first 4 timings for your memory, leave the rest on auto. Set your DDR voltage.

Manually set your CPU multiplier, leave the gtl reference settings on auto, (these mainly help quad cores) the other voltages can be left at stock until you get past 400FSB.

As far as overclocking goes, I always try to find out where my memory and motherboard maxes out first, I will set a 6 multi for the CPU, run the memory at 1:1 and start pushing FSB until I find the stopping point, should be around 430 on stock voltages.

After that I will find the Max of the CPU for the voltage I am willing to run using the highest multiplier and setting the memory divider low enough that it doesn't get in the way.

Once you find both it['s easy enough to figure out which multi to set for the CPU and what speed to run the memory at. Once you get that far you can start to dial it in.

If you need any more information or if I wasn't specific enough let me know.