Pre-RC2 and RC2
On July 7, 2001, Amazon.com mistakenly posted Windows XP for sale on its site, and included pictures of its box. Microsoft asked the company to take down the pages, which they did, although Amazon would later make the same mistake a day before XP was released to manufacturing. Amazon would later make another mistake when they revealed Windows Vista pricing before release.
Microsoft revealed that another interim release of Windows, code-named Longhorn, eventually released as Windows Vista, would follow Windows XP, moving the release date of Windows 7 (at the time codenamed Blackcomb) back at least two more years.
Build 2520 (with a build tag of main.010717-1624) was also released on the same day. There were no changes from previous builds although it was the first build to include the ability to remove Internet Explorer from Windows XP.
Build 2526 (with a build tag of xpclient.010724-1758) was eventually released as Release Candidate 2 (RC2) on July 27, 2001. RC2 didn't include any new features, although it had the ability to remove Internet Explorer, and this was the first time most users had seen it. Beyond that, Microsoft said that RC2 was primarily about bug fixes and fit-and-finish work.
Read more about this topic: Development Of Windows XP