The only thing you can really do to get more ventilation is to use a Notebook Coolpad (see Targus.com -- they also sell them at Office Depot, etc)-- these cost 29.99 retail (or less when on sale --I paid 19.99 after a rebate) and raise the rear of the notebook about 2 inches (or you can use 2 other settings that are lower).
This allows air under the notebook where the vents are and also gives you a typing position more like a desktop keyboard (slightly raised at top).
I use this with my Pentium M Centrino even though the fan is almost never on as I like the typing position, any spills to the left or right of the notebook will go under the notebook (spills on top will still go in) and you can swivel the notebook to any angle as well.
I have this year old laptop which runs with Pentium 4 and I notice that the fan does run all the time, after all it is a Pentium 4 laptop, but recently the fan gets really loud for a short period of time and then returns to normal. This happens a couple times a day. I put this laptop in a well ventilated area (by a cool window, that in the morning can get really cold and breezy) and yet it still gets loud, I have tried "dusting" it to remove dust and yet still nothing.