Using onboard video

I've got an old ASUS P4S800-MX. I'm trying to diag random BSOD'S that are mostly 8E's, 50's, and A's.. New harddrive 3 weeks ago, and the RAM is new (after getting free Kingston stuff). So what's next? I assume the video card. I have a Geforce in there but I want to bypass it and use the onboard video. Do I have to pull the vid card? I left it in and went into the bios and changed the settings to onboard video but it still ran off the AGP card. I thought if I changed the bios to do onboard, it would bypass the vid card but.........

thanks for any and all advice..........