HI, Chances are the noise you are hearing is a fan. I recommend that you open up the case and Blow the dust and dirt out of it. You can use canned air (expensive), lung power(not terribly efficient), small hobby compressor(my choice), or a vacuum cleaner with a plastic attachment for small areas. This is all best done in an area you don't want all the dust to be moved to and collect in. Once the major crap is removed, you can check which fan is the culprit by turning the system on and carefully holding a fan blade from spinning initially and listening for the noise and then releasing it and see if the noise level is different. There are Power supply fans, CPU fans and Case fans. You can do it by a process of elimination. You only need to stop the fan movement for a second or two. You do this with each fan till you find the noisy one. Actually, with the case opened you should be able to pinpoint which fan is the culprit much easier by just listening carefully. If you are not comfortable with holding the fan blade, one at a time, unplug the cpu fan and case fan from the main board or power supply and turn the system on for just a second or two and turn it off. You don't want the CPU fan to be off for very long (esp AMD Athlon products). Then plug it back in right after. Thanks and have a Great Day! Joe Lore ====================================== Hello. My computer is a Dell Dimension 8100, P4, 1.4Ghz, 384mb mem, 40Gb HD. I have virtually let this computer run non-stop since 2001, rebooting only periodically as needed, without problem. However, over the last few months I have started to shutdown each night because the computer is making a "fluttery, chirping" noise (best choice of words I can think of). Drive Integrity tests results and lack of hard drive problems have lead me to discount this as the source of the noise. I really think it is my power supply fan but that leads to my real question. Is there a way to know or test if my power supply fan is going bad before it is too late? Visit our website regularly for FAQs, articles, how-to's, tech tips and much more http://freepctech.com