LiveSide and Long Zheng both have good reports of a user on Neowin who is claiming to have installed an early external build of Windows 7, the sucessor to Windows Vista. I haven't been following the Windows 7 development all that closely, but I was under the impression that Windows Presentation Foundation would play a more prominent role in this release than it did in Windows Vista. It looks like Windows 7 will offer WPF-ized versions of the old Windows classics; Calculator, Paint, and WordPad.
In the more exciting news, it looks like Microsoft's internet services initiative has a big place in Windows 7. According to the early Neowin poster you can use your Live account to carry IE settings and favorites with you. Anyone who is using the Google plugin for Firefox that lets you do the same thing will know how handy that is. If they can take that and extend it to the rest of the platform (think Office documents, Video/Audio files) and then offer a seamless transition from web to desktop in some cases, it will be a very cool example of what I think of as the holy grail of RIAs - very similar experiences across a number of platforms with your data accessible in whatever form you need it (offline, online, etc).