Well i just upgraded my computer which I built 4 years ago with a new motherboard, processor, memory, video card, basicly everything except the power supply and the cd rom drive.
I put it together today and the computer screeched like a banshee. It let off this high pitched sound and I think i smelled some burning. It was only on for about 5 seconds. I refuse to turn it back on.
Newegg.com - GIGABYTE GA-P35-DS3R LGA 775 Intel P35 ATX Intel Motherboard - Retail
My power supply is an ATX-4OOW/P4. It has a 2x10 ATX which I beleive are in the right spot. (which I used the manual to check).
The motherboard only has 1 IDE slot so I had my cdrom as my main and slaved the harddrive. (I think that may be the problem)