well its an intel which doesn't get as hot as say an AMD so temp isn't as much of a problem (as much, its still a big problem tho!) and its a celeron so it wont OC very much to begin with, you might get it up to 3GHz. To OC go into the BIOS settings and chage the FSB. OC'ing is safe to a point, it can fry your system, can cause an unstable system, etc. if this is your first try at overclocking do some reading about it first.
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Overclocking - An Overview