Power Supply? Motherboard? Gfx card? WHAT?

was siting here on my computer doing everyday activities, (surfing
the net, music, not gaming- not anything difficult) When out of the
blue my computer just shut off- I thought the power was out or a surge
but my friends was running fine and the lights were all still on. So I
attempted to re-start it it come on, stayed on for about 5 seconds
before it just shut down again. Try-ed again 1 minute later, did the
same. Tried again 10 minutes later it stayed on but my monitor stayed
black, i checked the cables and everything basic but nothing. Then i
noticed a burning type of smell from my power supply.. not a good sign
i know.. I tried putting a new gfx card in there (a older one) and
still black screen.. dose anyone have any idea why it would be doing
this? Can just a bad power supply do that? Any comments would help,
Thanks

(my computer specs)

AMD Socket 939 Athlon 64 3500+, 2.2 GHz, 512KB L2 Cache 64-bit
Processor - Retail
ASUS "A8V Deluxe Wi-Fi" K8T800 Pro Chipset Motherboard for AMD Socket
939 CPU -RETAIL
ATI RADEON 9800PRO Video Card, 128MB DDR, 256-bit, DVI/TV-Out, 8X AGP -RETAIL
CCorsair Value Select (Dual Pack) 184 Pin 1G(512MBx2) DDR PC-3200 - OEM
200 Gig Raid Drive
With a 560 watt power supply