Interestingly CLauer thinks we develop Avalon on Windows XP... "My understanding is that the development teams that are working on WinFS, Avalon and Indigo are neccessary working on today's systems, Windows XP to name it. So, obviously, current pre-alpha builds of each of these three Longhron pilars have to run on Windows XP. I do not understand how it could be otherwise."

While the build lab does produce builds compiling on a shipping operating system (I actually don't know if they run Windows Server 2003 or Windows XP, but I think it is Win2K3?), developers run Longhorn.

If memory serves about 14 months ago it became a requirement that we dogfood Longhorn to use Avalon. For the first year or more of Avalon's existence Windows XP was the base we built on, however as we added more dependencies, and got more people using the bits, we could no longer support using WinXP as the dogfood environment, so we all upgraded to Longhorrn.

Of course, trying to develop a component and have your main dev machine be running a daily build of a pre-Beta operating system is quite a challenge. Some days you come in and upgrade to the daily build only to find that some core part of the OS decided to break that day. Of course, this is one of the ways we try to drive quality - by having the developers feel the pain if something is broken, generally it gets fixed very quickly. In addition even our VPs dogfood Longhorn, so you can imagine that occasionally there is a lot of pressure to fix something if their machines break!

The answer to the question is a little of both - we compile the new version of the operating system on both released Windows and Longhorn, but we only debug, test, and run (obviously) on Longhorn.