The most famous example of this is . Intended as the bridge between Windows XP and what eventually became Windows Vista, Longhorn went through a tumultuous development cycle between 2002 and 2006. During this time, the audio identity of the OS shifted drastically.
A paid soundpack would compete with free user-created packs. Microsoft Plus! for XP (which included sound enhancements) sold poorly. windows never released soundpack
Soundpacks such as the by MinderiaYoutuber serve as comprehensive libraries for this community. These packs typically include: Windows Never Released thoughts - Microsoft Q&A The most famous example of this is