If you search for utilities that do this, the articles/reviews tend to be back in 2003 or so. Likely because they don't work well enough to keep selling. The more portable apps the better since you can just move them and make a shortcut. Then reset the Open With if there's a registered file extension. Before attempting to move the whole thing en masse I'd be sure to have a backup image so I could get back where I started.
Googling I've seen a few detailed descriptions of how to mass copy stuff over and use links to get the Registry info to work, but most noted that things like Windows Update gets hosed.
If you try it, I'd have a way to back out of it. If you succeed it probably won't be on the first attempt.