I wanted to give reference to some interesting Windows sites I've come across in the last few years.
* Paul Thurrott's "Supersite for Windows"
If you need to learn how to upgrade your box to 7, or want to hear about the latest Windows gossip, he probably has it.
* Rafael Rivera's "Within Windows"
This guy started with publishing uxtheme.dll hacks to enable unsigned XP themes: he's still coming up with different things that are "under the hood" so to speak.
Pretty much a news feed on new software, with analysis. The forums are also littered with system tweaks and such.
I use this site when working on a Windows-based program: lots of resources for .NET development.