I can't count how many times a question like this has been asked here and on other forums...I've been answering this kinda question for a long time to people like you...
Don't get me wrong, this is a friendly community. But if you know nothing about overclocking, and if you are just starting please search around and read the already written guides on how to do it instead of making people write it all up all over again.
There are literally 10s if not 100s of guides out there all bout overclocking and on how to do it.
So having been here already before I want to point you in the right direction.
First of all, your system is a 2007-2009 era system. Core2 is kinda old having three generations of cpus already released after it. However, its not exactly a very bad system either. So if you're happy with the way it performs for the most part, you don't need to upgrade.
Second thing you need to know. You need to look up on how to overclock core2 systems. Also depending on the chipset from ICH7 to ICH9R
Read a few guides...watch a few youtube videos and try overclocking the system yourself. Make sure you have good cooling and that you don't go over the common reasonable voltage limits.
I would suggest looking up information on how to overclock by adjusting the FSB. That's how I overclocked my core 2 duo because I was limited in how high I can set my multiplier.
Also look into memory ratios because changing the FSB will also affect the RAM as well. Pretty sure the above guide mentions these things but you should definitely focus on it and look up more on it if you need more info than the guide has. Its a pretty good starting point though.