pc starts but wont boot

I agree, I know problems can occur out of the blue, but it just seems weird that removing cables and plugging them back in while doing cable management could have caused this issue.

What video cared do you have? Does it require power directly from the PSU and if so did you connect the cables with yellow and black wires to the video card? Low end video cards are powered completely from the PCI-e slot but more powerful ones require one or two leads directly from the PSU.

From post # 10

gpu:amd hd 7850 2gb gddr5

good news i found the problem at last,i went to a local maintainance store and it's engineer said that the whole mobo is fone except the bios,the bios needs recharging,so i sent it to the distribution agent to be checked and maintained,ty very much for your help guys i really appreciate it