Windows Longhorn is one of Microsoft’s most infamous canceled releases. This was meant to be the next release to follow up Windows XP, with a release date set for 2005. By 2004, the team working on Longhorn encountered several challenges, with huge ambitions bottlenecking its development. So much so, that work on this release was scrapped, and we ended up with Windows Vista, which launched in 2006 for the best laptops at the time.