Here’s an interesting interview with Mark Russonovich done by Paul Thurrott. Russinovich knows more about how Windows works than most people will ever know. What he talks about is a little on the under-the-hood technical-side but not too much. For example:

Paul Thurrott: So from an upgrade/migration picture, one of the easy complaints for Windows 7 is it doesn’t provide for in-place upgrades from XP. What went into that decision and what are the real issues there?

Mark Russinovich: Well, when you do an in-place upgrade, the test matrix for that is enormous. So, obviously, if we’re going to do an in-place upgrade, the most recent operating system is a higher priority than an older operating system that people are going to be coming from. From an enterprise perspective, it’s really not an issue because people don’t upgrade their systems, they do clean installs. From a consumer perspective, if you look at people running XP systems, they’re probably running older hardware that’s not even in the class of Vista/Windows 7 where it would make sense to do an upgrade.

In addition, if you look at trends in the past, consumers don’t upgrade either-they buy new PCs and get the new version of the operating system. So if you look at the return on investment of supporting the XP to Windows 7 upgrade path, versus the people that would actually benefit from making it easier than it is with the migration tool, it didn’t seem to make sense.