What a day yesterday, I'm a network administrator and had to call Dell out on TWO brand new servers, get home and my 8400 won't boot up.  Turned it on and the fan noise was just about deafening, and am getting what seems to be one long beep, 3 shorter beeps, a pause then 2 beeps.  I looked up the code for Phoenix and Dell and don't see that combination anywhere.  After turning the machine off and then back on a couple of times, the really super loud fan noise seemed to go away but it still seemed a little louder than normal and the beeping was still there.  I didn't feel like diving into a troubleshooting session as I had spent the entire day doing same, thought I'd post the problem here and maybe get a quick answer from someone else who's had the same problem.