Checked your specs and because you are using ATI Graphics, I have to ask....You didn't allow 'Windows Update' to update your ATI Graphics did you? If you did the drivers are most likely borked and will have to be reinstalled. Don't ever let 'Windows Update' your ATI Drivers.
Go to the XFX Website and get the latest drivers for your card and operating system http://xfxforce.com/en-us/Help/Support.aspx
If you don't know how to install ATI drivers get the Install guide as they can be tricky and you have to uninsall the old ones first.
Nice looking rig you have. First thing is unplug the power to the PSU and turn the PSU power switch off and then depress the start button for about ten seconds to discarge any residual charge in the PSU.
Then remove the 5770 and re-seat the card and then be sure the 6-pin connector from your PSU to the 5770 GPU is tight and hasn't been disconnected. Then plug in your PSU and don't forget to turn the switch back on.
Post back when your done.