The Windows Vista Release Candidate 1 (RC1) (built on August 29, 2006 with a build number of 5600.16384) was released to a select group of beta testers on September 1, 2006. On September 6, RC1 was released to MSDN and Technet subscribers, as well as registered Customer Preview Program (CPP) members with Beta 2 PID’s. On September 14, Microsoft re-opened the CPP to new members. The CPP ended on November 26, 2006.

The public release of Release Candidate 1 resulted in a number of extensive reviews and analyses on various technology news web sites, both immediately after its release, and in the weeks following. Ars Technica’s Ken Fisher wrote that performance had improved significantly over Beta 2, suggesting that faster machines may perform better than Windows XP; he also criticised the usefulness of the Windows Sidebar and the continued intrusiveness of User Account Control. CRN’s review noted five specific categories of improvements to Release Candidate 1: Installation speed, device driver support, performance improvements in several components, security, and multimedia capabilities. Criticism of Vista’s user interface arose as well, with Chris Pirillo describing the near-final state as “sloppy.”