Yesterday i tried installing a new video card (ati radeon 9550, to be exact) and after installation and hooking everything back up my computer wouldn't turn on. i figured it was my power supply, seeing how it was only 250 watts, so i went and bought a 400 watt power supply. so i hooked up the new power supply and it still won't turn on, i'm thinking it might be a problem with my motherboard or something. pc specs: hp pavilion a420n AMD Athlon(T) XP 3000+ 2.167 GHz 512 ram 160 hdd 7200 rpm crappy onboard video card (reasoning on bying a new video card) if anybody has any suggestion on repairing my comp, please tell me. thanks.