I don't know what to make of this. I was just sitting browsing the web on my MDD Dual 867 when I heard an extremely loud pop from the computer (it was followed by what sounded like hissing). My first thought was that the internal speaker had blown somehow (btw, I normally don't use the internal speaker, I have soundsticks). But the internal speaker is fine and so are the soundsticks and iSub. So the next thing that I did was pop the side open, very carefully so as not to touch anything, but I didn't see anything apparently wrong with the inside either. My next thought (and current theory) was that something inside of the power supply had blown. Btw, I have the power supply/fan upgrade. Don't know if that means anything. I am a very experienced mac user so I know what I'm doing, but I don't know what to make of this problem. I shut it down almost immediatly to let it cool off, but it's up and running again and it seems perfectly fine. No wierd stuff happened when the pop occured either. It's a mystery. What should I do? Should I replace the new PSU with my old one (I kept it.)? *edit* oh yeah, It's running F@H nearly 24/7 on both processors so it does get a little hotter than most dual 867's if that means anything... If it means anything here are my specs: PowerMac Dual 867 MDD (purchased in February) 768MB DDR2100 RAM 1x original 60GB IBM Hard Drive 1x 120GB Western Digital Hard SE Drive Original 32MB GeForce 4MX Harman/Kardon Sounsticks Original Combo Drive External Que! Fire Firewire CD burner NEC MultiSync 1760v LCD monitor attached via VGA airport card OS 10.2.6 Help me please.