BSOD on boot x32bit

HI this is my first post I realy REALY need help.just morning i was just photoshopping with CS4 and when i minimized application i realized that the desktop home screen was frozen and i couldnt click on internet explorer like if it where a wallpaper but i saw that the start button was fine to i went to start and to internet explorer checked my email and about 10 min later i closed the explorer and the home screen was still frozen... so i restarted my computer,once it was booting up on the windows loading screen (the one that says microsoft corporation) the green loading bars that move stopped moving and a blue screen of death appeared for like half a second and went away.My comp automticlly restarted and when the windows error recovery page came up i chose start windows normally and one it was loading... it happened agian wit a flash of the BSOD and a auto restart. ive tried safe mode,windows CD repair but says that it could not find anything tried sys restore... I have no restore points. Every time it start it happens.

please help me

BY THE WAY MY COMPUTER WAS BUILT NOT BOUGHT

dave

intel core 2 duo @2.4ghz
4GB of DDR2 800HMZ
windows vista home prem.x32bit
xfx geforce 9400GT
160GB western digital HD
ASUS cooling fan

Please get a start on the stuff here: BSOD troubleshooting preliminaries - Vox

And, please perform an analysis of the memory dump file(s). You can do that by following the instructions here: Diagnosing Bsod's (originally posted 02Oct08) - Vox

I realy cant get any help on it, keep in mind that i cant boot whatsoever.
Ive tried everything i can possibly do... but, i was thinking on changing the video card back to the old one. just 2 days ago i have recently change my Geforce 8500GT to a 9400GT is that what caused this??? plz tell me so i can change it.