Overclocking is manipulating your system so that (in this case) the cpu runs at higher
clock speeds than normal and gets workloads done faster/more smoothly.
There are several ways to overclock a cpu(change multiplier, base clock or both). Since your
e7500 is multiplier locked(you can't raise the multiplier, but you can lower it) you will be
restricted to using base clock changes. That cpu should be able to overclock quite well, but
you need to have both a motherboard that will let you make changes to base clock speed
and cpu voltage and high speed ram that won't go out of spec when you change the base
clock. What motherboard do you have(brand and model)? Do you have ddr2 or ddr3?What
speed is it(ddr2 is either 200 base/400 double data rate, 266/533, 333/667, 400/800, or
533/1066. ddr3 is either 400/800, 533/1066, 667/1333, or 800/1600 in your case)?
Raising clockspeed alone creates a linear increase in power use &c raising voltage creates
an exponential increase in power use. More power used dissipates more heat. therefore,
a high overclock is also dependent on the level of cooling you can give your cpu. The stock
intel heatsink won't be good for a high overclock. You should probably have a good tower
style heatsink fan, but something like that may or may not fit depending on your mobo
layout, ram height(tall heatsinks) and the dimensions of your case. Can you tell us what
brand and model of ram you have and what case? Maybe post pics or links?
If we know you have the tools to overclock or can get them, we can advise you on more
specific methods to ramp up your cpu speed and test for long term stability. The max
safe temperature and voltage vary from one class of processors to another. Kind of a
general rule is to not exceed 110% of stock voltage and/or an increase of .1 volts(again
depending on the cpu). I will go ahead and say a popular method of testing cpu stability
is to download for free, install and run prime 95 with all cores loaded (a higher workload
that your cpu will likely ever see otherwise) and check for temps(download speedfan) and
errors in the test. Maybe increase the base clock 5mhz at a time(55mhz cpu clock change
(inserts a wedge into this wall of text)
on your cpu with the max mulitplier of 11) and test for 20 minutes noting temps and
looking for errors. If good, raise base clock again and retest. Stop when you get errors or
unsafe temps. Maybe set the fan speed on the cooler to a noise level you can tolerate
first thing so you know the limits of your cooling. If you get errors but temps are ok, nudge
the voltage and test again. Your cpu could reach 4ghz with something like a combo of
a 10x multiplier and 400mhz base clock using either ddr2 400/800 or ddr3 800/1600 that
you first lower to 266/533 or 533/1066(oh yeah, mobo must allow ram ratio adjustment
as well) and letting it come back into spec as you raise the base clock from 266 to 400.
Sorry that last bit was a small wall of text. I hope this answers some questions without
creating a bunch more. And please post some more specific specs on the parts of your kit
that I mentioned. Also, tell us how many amps are on the +12v of your power supply
(if you don't know, check the label). That is the single most important spec of a power
supply and may affect your ability to get a good overclock that is safe and stable(the
added power use of an overclocked cpu versus one at stock speed/voltage will of course
place a larger burden on your power supply).
Edit: I started typing this before you posted that extra info. Give me a bit to do some
googling and I will get back to you with more details soon.
Also, that variable multiplier is typical. 6x for light loads/desktop idle, 11 for games etc.
Edit: After a look on intel.com at your mobo, it has what I feared is a g41 chipset with
integated graphics. Your options for making changes in the bios may be limited. You
can reboot and take a look at the various screens in the bios to see if any of the
previously mentioned changes will be possible. Otherwise I suggest you google setfsb
and overclockulator and read about them and/or install and run them to look through
the options. They are supposed to let you overclock with software in windows instead
of using the bios but you want to make sure you can make other changes like locking
down the pcie bus speed or manipulating ram ratio/locking its speed so that any
attempts by you to overclock with the program won't throw your system out of whack.
Edit: forgot to mention that the pic I saw of your mobo showed a fairly tall north-
bridge heatsink that could get in the way of some larger air coolers.