Hello,
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"Longhorn" was actually the codename for what we now know as Windows Vista during its development phase. Microsoft often uses codenames internally for projects before the final product is released and named officially. The codename "Longhorn" likely started as an internal way to reference the project and, once it was ready to be released to the public, the more marketable and official name "Windows Vista" was chosen. This practice helps create a clear and distinct identity for the final product, separate from its development phase.
I hope the information above is helpful.
Best Regards,
Yanhong Liu
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