psu failure

I recently acquired a new mother board (asrock 4coredual sata2 and pentium d 840 3.2 ghz processor and put it together with a radeon hd 4650 agp graphics card with 400watt psu, I started to install xp home edition. every now and then a slight burning smell would occur then stop during formatting the hard drive then agfter the normal computer restart to continue installing everything was normal then suddenly (i think it was about to request the serial key) the psu popped and then the pc switched off and the supply failed. is this likely because the psu was overloaded and I need a higher wattage/ampage for it, its an old one that had was used on a pc single core athlon processor 64 at 2.4 ghz +3700. the ram and video card was the same but I notice the pentium d requires a highr wattage. I am aware of the need for high quality psu's so i just want to know if its because of lack og amapage (12v was putting out13 amps)

the heatsink is brand new could that be source ofslight burning smell?

My guess is a cheap nasty psu, although it could also be just an older design that didn't have enough 12v output, ether way that was probably the main source of the smells.
Probably from the capacitors boiling and leaking.

It wouldn't be a heat sink as there's nothing on there that should generate a smell.

400w should be plenty for your needs, the issue with psu's is quality not wattage numbers, there are many ways in which psu companies/brands can fudge the numbers, very cheap psu's can often only provide around half the actual listed wattage.

it was a very old psu probably lasted longer than it should have

I feel you pain, I had a similar problem once, change the PSU before it causes damage to other parts!