Using an old HDD with Windows 7, will I need to reinstall?
I have an old HDD that I'm reusing, will I have to reinstall Windows 7? Last time I used it, it has the OS on it.
If you are going to a really different machine it is best to plan a new install, or at least a full repair installation: http://www.sevenforums.com/tutorials/3413-repair-install.html
Windows 7 is a lot more forgiving than earlier systems, but if you change everything but the HDD I would back up all your data and plan on a repair install, but plug it in and see if it will update to the new system -- sometimes it works and sometimes it doesn't. Expect that you will need to do at least a repair install and probably a total reinstall and you will be fine.