|set too active, the processor will slow, but your not likely to notice, thus it will stay cooler, and the fan will not have to work so hard...close all extra process's like indexing and search, which may set to run when the system is not in use, check the settings for anti virus, when it runs etc etc..|
if your fan is running a lot, and its an older computer you should try a can of compressed air and blow out the dust, or vacuum all the vents, it may be that you need to reseat the cooler and put on fresh thermal paste..
if its new take it back to the shop and ask them to this for you.
i hate computers!
but cant help myself....