if it's vista you can go into power options,can't remember exactly how to get to the processor options but you can change it to run at say 80% maximum and that should stop the fan being on all the time.
If this is a recent problem and you (or you gf) haven't made any changes in BIOS or power options then i'd ask why it has started....dust ingress is commonly a cause. In that case it needs cleaning out!
Before you reduce the fan speeds (which I think is what smackheadz's post was implying, I'd just check to see what temperature your processor is running at. If it is running hot then reducing the fan speed could cause damage.
Download and insntall Realtemp (click here). It's free software which will give CPU temperature info.
If you can post back and say what CPU it has, looking up its max operating temp is a quick job. Will post links to the relevant place.
sorry i'm not great at explaining things.when i had vista i could change the maximum processor state from 100% to whatever you wanted to.i think it was control panel-power options-and change plan settings or similar.but not changing the fan speed.