you can't overclock 4 dimms very well, so forget memory overclocking, and you have a CPUwith a locked multiplier (can't go faster than stock, but you can slow it down).
So your only easy choice is to up FSB by 4-12 mhz at a time in BIOS then reboot to OS and do stability tests (like 3Dmark or PCMark)
BSOD's mean you should check for CPU overtemp issues.
RAWR!