So I've just bought a new computer and replaced everything but the hard drive from my old build. My new PC boots up but goes to Windows System Repair and says it can't start up my computer. It is a SATA 3 Hitachi HDD that has Windows 7 and many games in it. Ive backed up most of my things in an external hard drive. How could I use my hard drive on my new computer? I don't have the Windows 7 system disk. Could I make one by putting it back on my old hard drive? Thanks for answering.