Windows 7 installation

[akwaboah37]

I have installed Windows 7 on my Windows XP it worked before buh now I tried again and after the installation when it was about to restart,it went off and switch on again but want come,the machine is on just like that

 

[hang-the-9]

Not sure what is happening, the computer won't turn on? Or turns on but Windows is not loading all the way? Need to post exactly what is happening after you hit the power button, how far does it load, what screens come on. Also need to list system specs including power supply brand and model.