"Blackcomb" was a code name for a Windows release.
Windows Blackcomb was originally announced as a successor as Windows XP.
Web Services Integration
It was intended to include major features such as integration with many web services
Advanced Storage System
It was also planned to include a advanced storage system
It was planned to have even more stuff than what we have listed here.
However, Microsoft realized that the development team of Blackcomb could not hit the expected release date so they postponed it. A while after that, another project called Windows Longhorn acquired many features from Blackcomb, so it got postponed even more.
A little while after Microsoft announced that the server version of Windows Longhorn would be discontinued, all the ideas were mostly used in the same project that acquired many features from it earlier, called Windows Longhorn.
When Windows Longhorn was being finished, they renamed "Blackcomb" to a new code name called "Vienna".
A little while after that, the project was cancelled and replaced with a new code name called "Windows 7".
There are no known builds under the code name of "Blackcomb".