PC wont boot when i run my gfx card

[matt12343234]

hi there my pc config is
Phenom II 940
Asus M3N78 EM
2 X 2 DDR2 800
2 X SATA HDD
Palit 4850 sonic
Tagan TG500 U37 PSU

my prob is that when i try to run my pc with my palit 4850 sonic gfx card...my pc wont boot...some people suggested me it could be due to psu so i even got a new tagan tg 500 u 37 psu but still the problem persists
my pc boots perfectly well when i run on onboard gfx
prob come only when i try to run the gfx card on my mb...most of the times it doenst boots
can any one please help me determining what the real prob could be

 

[netxuser]

it looks like there is a conflict with the onboard video card and your new video card, try to update your bios, and try to disable the onboard video card when your using the new one.

 

[swifty_morgan]

Go into the bios and look for the graphics. Set it to auto or for pci/peg slot. Try moving your wires around. That psu has 2/18a rails. If you switch cables around you might get lucky and get enough power to "one" rail and get more juice to the card.............. high amp Single rail PSU's rock. ......too much marketing hype on multi rail.

 

[megamanx00]

Ack, GeForce 8300 chipset. First go into the BIOS and disable the onboard graphics, then put in your new GPU and try to boot up. Since it's an ASUS I'd suggest updating your BIOS and googling "Asus M3N78 EM Radeon 4850" to see if anyone else has that particular problem. It could just be that you need to update your BIOS, but you should also check your Radeon 4850 in another system to be sure that you don't have a faulty video card. It's rare but every now and then you get a video card that's DOA.