Gotta read dude. Sorry but that's about all the advice I can give. Just google "cpu core2duo overclock" or similar and take notes on what other ppl do. If you don't wanna read a whole lot or have time to, then maybe overclocking isn't for you? If you forget some important part or get impatient its a really easy way to make a cpu into an expensive paperweight.
Besides e6600 is fast already...overclocking (to me anyways) is best when you got an old or cheap processor and clock it into 'brand new expensive cpu' status. Before this processor I got my best oc's with an old celeron and a certain stepping 1700xp processor, which made both fly even tho they were gettin on in years. When yer e6600 is no longer one of the best out there, that's when you should start thinking about serious oc'ing.
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