Its possible the ball bearings on the case fans you have are going out. It will make alot of racket when that starts happening.

Only other thing that would be likely is your hdd, but you would be noticing other things happening as well if your hdd was starting to go out and make enough noise that you could hear it. Its more likely that one of your fans is starting to die, which isnt all that uncommon, especially if they use cheap fans.

You are talking at best, $15 to replace the fan, and thats including shipping.
imitator Reviewed by imitator on . I need someone who knows alot about Dell comps I have a year old Dell XPS 400 and now about once a week there will be a loud hum coming from what sounds like the fan in the front of the computer. Weve cleaned all the dust out and it still dose it anyone know if this is bad or what the hell it is Rating: 5