I bought a Dell Dimension 3100 last May. It is very noisy. When I reach down to the vent at the back of the case, I felt the wind blown all the time. Searching by google shows different answers. A few of them are:
* CPU heatsink fan is a noisy cheapo
* case fan is a noisy cheapo
* the cooling is not adequate thus the fan has to be on all the time, due to inadequate power supply?
anybody has any experience to pin point the problem ?
How you revised the BIOS, Ive find somes times BIOS with a control opcion about fan function . (Quiet , Always)
Take care about be in the BIOS if you are not sure abour something , dont do it!
In the other hand your dell is on warranty . What happend?
Did you call to support Dell?
Just remove the side panel and while it's making noise touch each fan to make it stop spinning temporarily and see if the noise goes away. You should be able to isolate which fan is noisy this way.
If your computer is still under warranty, I wouldn't recommend this as some manufacturers will void the warranty if you remove the cover (I don't know what dell's policies are).
Sounds like you have some funky bearings on either the processor fan or the power supply. I found out the hard way that its not always best to blow out a fan with the compressed air, because sometimes you can get the dust forced into the bearings and making things worse.
This is more usefull on laptops but it may work for you. Put some random pice of junk to act like legs or supports under your computer so heat can escape the from the bottom. Also if its against the wall you might want to move it away so air can get away from the side.