About two months ago I cleaned out my entire computer of all dust and things like that. Ever sice then, my computer, possibly the fan, has been making a sort of chirping sound. Almost exactly like a cricket. I opened my computer again to see if anything was rubbing up against the fan, but I couldn't see anything. For some reason after I did that, the noise had stopped for about three weeks. Now it is back to haunt me. What could it be? Has this happened to anyone else? I can't concentrate or sleep well at night from this annoying noise.