Hi there,
I’ve seen the question come up a couple of times on the answers.unity3d.com site, as well as elsewhere, so I figured I’d try to answer it myself.
Lots of people seem to have a gripe with the default path chosen for new Unity projects when you create a new project, so I poked around a bit and found how to change it.
I blogged the instructions here: http://www.dociletree.co.za/adventures-in-unity-how-to-change-the-default-new-unity-project-path-in-windows/
It’s really as simple as changing a single registry entry.
Hope this helps people going forward.
-DWN