That is a hard issue to walk someone through on a message board. Off the top of my head I would say manually pull hard drive and use another computer (I use a hard drive dock station as long as it is a sata connection and not an ata) to copy documents and media you don't want to lose. Then you are going to have to erase the Hard Drive and re-image the OS to the Hard Drive and make it bootable using a bootable usb. Then you will still have to figure out how to activate the OS (different depending on what version of windows you have/want). If you are familiar with bootable usb's and Linux OS's then you can try and run Ubuntu (or other Linux OS) on usb drive to diagnose the internal hard drive before pulling and re-imaging. That requires a little more computer "know-how".