You haven't tried replacing the most common part to fail on PCs - the PSU (Power Supply Unit)! The symptoms you describe are typical of how PSU failure often becomes evident.
No, I just checked the psu with another pc and it's working... I don't know what more do
Just because the PSU from this PC works with another motherboard does not mean it's definitely OK with yours. PSUs can be a bit temperamental and sometimes behave differently when hooked to motherboards with different characteristics and power requirements (especially if they're already marginal when it comes to being within voltage tolerances).
A better test would be to find another PSU to test with THIS DG35EC motherboard. If you want to avoid buying one just for testing purposes, a local computer shop may have some they can try with your PC for a small cost just to see if that eliminates the problem.