During the Longhorn project (before the reset to use Win 2003 code and create Vista from it)... There was plans for a "Castle" feature which would allow you to roam your profile, data across multiple PCs in the home. Parts of castle made it into Win7 homegroups later, but it was very much scoped back.

At the time I was in the WMDRM team which handled content licensing. We had a feature that built on Castle if you purchased audio/video content (purchased music still had DRM then) we'd automatically roam the content licenses among all the PCs in the home. We had the typical challenges from content owners that this could be used to share content in a dorm, over the internet. We had to design in things like proximity detection to ensure you aren't sharing beyond a home network. It was somewhat complicated (DRM couldn't be simple), but it would have provided a far better user experience.

We also planned a centralized DRM licensing backup/restore service so you weren't beholden to the service you bought content from deciding to let you have another license years later.

All of this was cancelled with the reset unfortunately...