Making headway with the development of the first service pack for Windows Vista, Microsoft has made available for download a new testing milestone of the refresh. On November 14, 2007, the upcoming service pack for Vista evolved into the Release Candidate phase. However, as the label of the testing build indicates, the fully fledged RC is yet to come, as Microsoft is offering just a taste of the Vista SP1 Release Candidate. While initial reports related to the development of Vista SP1 pointed to the availability of a public version concomitantly with the first Release Candidate stage, this is not the case. But Microsoft did expand the testing pool in comparison to the beta launched in the last week of September.

Windows Vista Service Pack 1 Release Candidate is build 6001.17042. Vista SP1 RC is up for grabs for over 15,000 testers. The first beta for the service pack was dropped into the laps of in excess of 12,000 testers, on September 24. Vista SP1 Beta Build 6001.16659 shipped only to participants in the testing process of the development milestones of Windows Server 2008 and Windows XP Service Pack 3. Vista SP1 RC can also be accessed exclusively via Microsoft Connect, although the Redmond company did slip up and produced signs indicating that the build would be opened to all MSDN subscribers.