I had a hard drive with windows 7 on it and it worked fine. Then some time ago it went into a infinite loop. I tried to run system repair on the machine but it didn't load. The same thing happened when I tried to go to the installation set up. I knew the disc was fine because I tested it. I took out the drive and put in another spare one I had. With the spare drive it let me open system repair and the installation setup. So I installed windows and once I added back the old drive, windows did not start. It was stuck on the "windows starting" screen. So I took out the old drive and it boots. The old drive is readable in the bios but it somehow is preventing the drive from starting windows and launching system repair. I tired plugging in the old drive while windows was already running but it didn't pick up.