From the node.js blog:
I’m pleased to announce that Microsoft is partnering with Joyent in formally contributing resources towards porting Node to Windows. As you may have heard in a talk we gave earlier this year, we have started the undertaking of a native port to Windows — targeting the high-performance IOCP API.
This requires a rather large modification of the core structure, and we’re very happy to have official guidance and engineering resources from Microsoft. Rackspace is also contributing Bert Belder’s time to this undertaking.
The result will be an official binary node.exe releases on nodejs.org, which will work on Windows Azure and other Windows versions as far back as Server 2003.