i just recently overclocked my e2180 (its also a core 2 duo)
to overclock mine when the pc started up i would press delete go into the bios go into a thing called MBIntelligent Tweaker.
most core 2's have a locked multiplier mine was locked between 6 and 10 its default was 10.
you cpu speed is your multiplyer x your front side bus (fsb) mines stock is 200 so 2ghz i overclocked it tp a stable 260 to get me 2.60ghz.
first off all my other settings where set on [AUTO] so most of them changed depending on what i did. when i increased my fsb it automaticaly increased my voltage a bit as well as overclocked my ram.
you might want to try and set your ram and voltage to stay on their default settings overclocked ram can get unstable and higher voltages make it hotter so if you can avoid that its good but if you leave voltage on auto it should be fine if you have ok cooling.
all cpu's are diferent even same make and models overclock differently somthing to do with the quality of the silicone in them which varies so you might only get up to 2.5ghz while someone else with your exact same specs could get like 4ghz.
overclocking means your hardware wears out faster,uses more power which causes it to get hotter which leads to it wearing out faster again. you can also damage your motherboard overclocking and possibly your ram.
some people saying stuff about your ram should be 1:1 with your fsb so 2x fsb=ram so 400fsb would be for 800mhz ram, im not sure what the deal with that is i think it makes t a little more stable or somthing or gets unstable at bad ratio's anyway mines at 3:5 and seems to be fine i recomend you try and get 1:1 tho.
i use prime95 and leave that on for about 24 hours if it has no errors your overcllock is stable.
i used realtemp to monitor temperatures.
and i used cpuz to check lots of my specs and how the overclock worked on my things.
thats all i can think of good luck