do it only if u r a professional.. assuming that the system bios hs not been flashed or updated in a wrong way..if so u gotta replace the m/b.. 1st check for ac main supply and fuse..next check all the outputs of smps viz. 0v (black~ground); +12v (yellow); +5v (red, green~ps-on, violet~pg & grey~sb); -12v (blue); -5v(white); +3.3v(orange)..if faulty try repairing or replacing the power supply with a standby n see.. if all above are ok..check the cmos/system battery..(above +3v).. check the cpu fan rotating and the cpu generating heat..try replacing the cpu with a standby (if no heat is generated).. there may b a chance for m/b's crystal clock generator to b faulty..try repairing or replacing the m/b with a standby.. hope it'll b enough to solve ur problem.. seek professional assistance of ur system admin/vendor....
as i understand there is no power on your system motherboard so u need to check the power cable and monitor cable otherwise one simple resolution is check smps.. otherwise if your system is in warrranty so u can call to technical guy..