Black screen after bios logo

Hello

Yesterday i bought a new power supply (corsair cs650m), and after i replaced it my pc stucks at black screen after the bios logo when i turn it on.

My specs:
Intel core 2 duo e6700
Evga gts 450
2gb ddr2 800mhz
Asus commando
2x 250gb hard drive
Window 7 32bit

What i tried:
1. I replased the power supply back to the old one with no results.
2. I moved the video card to other slot.
3. I moved the ram to other slot and tried to run it with 1 stick of ram.
4. I chenged the sata cables and connected them to othe slots.
5. I tried to run windows installtion from usb but its still gets black screen.

Safe mode also doesnt work.

When you say "Safe mode also doesnt work", do you mean that you get the menu in which you can choose normal/safe mode and in then says starting Windows and after that turns black?

If you do not get as far as the boot menu/starting Windows screen and literally a blank screen immediately after the bios, disconnect all the drives from the motherboard to see if you now get the "non-system disk or disk error, replace and..." message. If you do, reconnect the drives one by one until you figure out which one is causing the problem.

With apologies if you have done already - have you double-checked all the connections? It sounds like the hard drive with your OS on it is having a problem. The best of us miss stuff like this - I took apart a friends' laptop that wasn't working, couldn't find the problem, and after literally hours scratching my head noticed that I'd dislodged the ram sticks. If you have access to another computer, try putting in other hard drives (with both PSUs), and then a usb boot stick.