Move an Old Hard Drive to a New PC

Trill asked the Hard Drives, NAS Drives, Storage forum about moving the hard drive from an old PC to a new one, then booting Windows XP.
Moving an existing Windows installation to another PC is a massive pain. When you install Windows onto one computer, it configures itself for the hardware. If you move the hard drive with that installation to another PC and boot from that, the OS suddenly finds itself in hardware it doesn't understand. It's as if you woke up one morning and found yourself in a strange house and had no idea why. But Windows isn't as smart as a human being. You would find the bathroom, but Windows would just take the same steps and turns it does every morning, and walk into a wall.
Then there's the licensing issue. Windows is copy-protected. It won't work on hardware too different from what it was installed on. If you have a retail version of XP, that won't be too much of a problem. You call a Microsoft 800 number, explain your situation, and they'll fix it for you. But if XP came pre-installed on the old PC, that's the only PC that copy can run on.
Besides, what would you do with the old computer? It's worth a lot less without a hard drive or an operating system. True, you can set it up with Linux and not buy an OS, but you'd still need a hard drive.
You're better off buying a new hard drive and Windows 7--or buying a PC with them included. Just make sure you migrate your data files to the new PC and properly remove them from the old one before you get rid of it.