You have mis-matched ram, not a good idea. Make sure they are set to the lowest speed (1333)
Yes of course you can overclock it. What cooler do you have. If you have a decent one try this
multiplier 9.5
fsb 400
cpu voltage around 1.3
change the ram ratio so it is close to or below 1333mhz
do not touch any other settings, save and exit.
This will give you 3.8ghz quick and easy. That cpu can do much higher speeds, possibly even up to 4.6ghz with some tweaking and if your motherboard can handle high fsb. You should easily reach at least 4.2 though, try the settings above first and see how it goes.