Problem with my video card loading. PLEASE HELP

[firstinlastout]

so i've had this problem for a few days now. when i restart my computer with my monitor plugged into my radeon 6870 the screen wont load up. so i restart it with my monitor plugged into my onboard and it will show up, then i plug it into my radeon again and now it works. but also when im playing games it will shut off. so i restarted and it wouldn't load up on either. no beeps no nothing either. my current mmobo is a asus m4a78t-e

 

[echod]

Make sure your drivers are up to date

 

[13thmonkey]

what PSU?