My desktop pc doesnt start anymore

Hi,

Few days back my desktop pc turned off suddenly. and its not starting anymore.
Try to switch it on but the power doesnt seem to work. The mother board light is on when i plug the wires but when i press the power button to switch the pc on the fan doesnt start. Dont know whats the problem. May be the" power sw" wire that comes from the power button to the mother board is not workin or else.

Tried using my hard disk in friends pc but hardisk doesnt seem to work. I can go to the bios and modify changes as well also the the pc detects the keyboard and other stuff in the start but doesnt load the windowsxp anymore and keyboard also gets stuck after wards when i select to start window from the options below

start window normally
safe mode
safe mode with cmd
safe mode with networking

when i select one of these options the screen becomes black and their is a bar that load sin the bottm. but then windows logo doesnt come and it stucks.

What can be th problem. Plz guide me with this