Bad Luck with my PC...Plz help :(

Since the begining of this month (MAY) , I started to get "BLUE SCREEN OF DEATH or BSOD" , when I play games or other heavy duties And sometimes in idle. I re-installed XP by thinking it was an OS issue. But BSOD continued with freezes and crashes.
From the past 1 week, Whenever the computer starts, atleast 1 of the hardware won't load its driver. For eg: Videocard, Soundcard...etc. If they both load their drivers, AVG Antivirus doesn't work. Guessing that it was a virus, I tried to re-install AVG, but during the next bootup it won't go beyond the windows loading screen and simply restarts! Then I thought of re-installing XP, but during installation it won't copy some of the files from the CD to Harddisk. Tried it with another CD, didn't help! Got another CD-ROM and tried, didn't help! Finally I installed XP through network!!! And What? Antivirus won't load during start-up...Most of the softwares can't be installed as their services couldn't be started/loaded...
I couldn't take it anymore!!! I got memtest86 on a floppy and checked for RAM errors....got a hell of a lot of errors on it...I was very happy to find that and went straight to the shop to get a brand new ram. When I came back and pressed the power button the comp, It just wouldn't switch on (this is even before opening the case or putting the new RAM). I opened up the case to see what was going on inside and guess what I found??? SMOKE!!! coming from Motherboard!!!
Now Tell Me , Who Was The Real Culprit Here??? Motherboard/PSU/Memory/Harddisk/Processor/Videocard ???
Please Help!!!




Specs:
Processor: AMD Athlon X2 4400+
Motherboard: Gigabyte (GA-M55S-S3) [Nforce 550]
Videocard: Powercolor Radeon X1950 pro 512mb
Harddisk: Samsung 200Gb
RAM: Corsair 1024mb 667mhz
PSU: 450W
OS: Windows XP

what brand was that psu? my bet is the psu, it is probably a cheap one that overvolted or something alike causing slow damage to your components to eventually kill them. or maybe you have shorted something along the way but you say that the smoke came out before you messed in the case. the only thing to try now is to test your pc with an other psu, if you are lucky maybe the only dead compenent is the psu but i doubt. test each parts.

RIP...

POWERMAN
Model no: IP-S450Q3-0
450W Output


is that a crappy brand???

never heard of it so it probably is. but never mind that, like i said try an other powersupply see if it works.

Spend a few bucks and get a decent mobo...pull your RAM, CPU etc...transfer them over...just to be on the safe side, include a new power supply...Gigabyte is a good product, but thats not saying you can't get a bad one occasionally.