So I take my 'puter to get a new motherboard. The place says okay we fixed it! Got it home, it fired up once. Took it back and four months later they said "we'll find one just like it and sell it to you". I said fine, unwillingly, but told them I wanted the OS from my hard disk on the new one. I expected them to clone my hard disk to the new one. What do they do? Put a pro version of the OS I had on the hard disk with that hacker proggy kmsauto. Piss me completely off. I have zero spare dollars to buy an OS much less a new computer. What would be the best way for me to get my old legal version of the OS onto a new hard disk so I can stop using an illegal copy? I'm okay with cracked software and stuff- just not the OS and not when I didn't ask for it. Know what I'm sayin'?
Do you still have access to the old hard drive? Will it not fit in your new computer? Or you could image the old one and put it on the new disk. If you need an OS to do this I'd use Linux Ubuntu or Mint booted up on a USB stick or CD.
dd is the command you are looking for in Linux.
If the two hard drives are different sizes you'll probably need to adjust the partitions afterwards.