Cpu lead power not getting on

hi everyone i have spent lots of money repairing my pc. I went to so many service centre but could get my pc work like how i bought it for the first time. Now i bought new motherboard, processor, hard disk, and dvd drives. Only cabinet is the old one. Now the problem is i installed windows 7 and when i run for the first time the audio sound is coming and later when i on my pc no sound is coming so i went to a cyber cafe and download all sound drivers for biostar motheboard in which there include a bios updates software, after installing all sound drivers still no audio output so i installed bios updates and when it reach to 95% it got hang for over a period of time so i press the restart button suddenly my pc is not functioning , processor fan and dvd drive is working but cpu led power is not getting power on and my monitor too is not displaying anything, m really exhausted n sick on other hand my exam is approaching so its a badly needed for me, how do i rectify the problem, someone plz plz plz help.