By August 2004, Microsoft has already missed their initial Longhorn ship date and even their PDC 2003 era Beta 1 date. However, Longhorn was approaching feature completeness. However, they still had a major milestone - WinHEC 2005. While at the time of WinHEC 2004, Beta 1 was supposed to come out in February 2005, a small delay would be acceptable given the unexpected difficulties in componentizing Longhorn. Assuming they had to be done by March 2005 (given the show in April), that gave Microsoft roughly eight months to get Longhorn together and in a semi-shippable state for WinHEC 2005.
Longhorn's speed/stability issues by this point seem to stem from just a few major causes
- The WinFS indexing service was very demanding and not-yet optimized
- The componentization had introduced extra steps to setup and removed core features
- The .NET Framework 2.0 on which WinFX was based was still unfinished, causing memory leaks, particularly in Explorer and the sidebar
- Multidirectional dependencies between Managed and Unmanaged code