In the ever-evolving landscape of Microsoft’s operating system, few builds hold as much sentimental and technical value as Windows 10 Insider Preview Build 21390. Released in the spring of 2021, this build represents the end of an era. It was one of the final "Windows 10" branded builds pushed to the Dev Channel before Microsoft officially unveiled Windows 11.
For enthusiasts, archivists, and IT professionals, the search query "Windows 10 Insider Preview build 21390 x86 x64 ISO incl" has become a hot topic. Why? Because this build is the last version of Windows 10 that retains the classic Start Menu, taskbar, and context menus without the drastic redesigns that came later, while still incorporating cutting-edge performance improvements.
This article provides a comprehensive deep dive into Build 21390, covering its features, system requirements (x86 vs x64), how to obtain the ISO (legally), installation tips, and why this specific build has gained "cult classic" status.
Build 21390 introduced an updated Settings > Personalization > Fonts page. It allowed drag-and-drop installation for multiple font files (TTF, OTF), a massive quality-of-life improvement for designers. windows 10 insider preview build 21390 x86 x64 iso incl
| Feature | Build 21390 | Windows 11 (latest) | | :--- | :--- | :--- | | Start Menu | Left-aligned, Live Tiles | Centered, static icons | | Taskbar | Never combine, ungrouped | Locked grouping, no never combine | | Context Menu | Full classic menu | "Show more options" extra click | | Drag to taskbar | Works perfectly | Broken (fixed in 2023+) | | Security | TPM optional | TPM 2.0 mandatory | | Android apps | No (no WSA) | Yes (via Amazon Store) | | Performance | Snappier on old SSDs | Heavier animation framework |
| Issue | Solution |
| :--- | :--- |
| Windows Update stuck checking for updates | The build is expired. Disable Windows Update service. |
| Store apps won't download | Microsoft's Store backend no longer supports this old Insider branch. Use offline installers (e.g., winget via command line). |
| Dark Mode toggle missing | Re-enable via Registry: HKCU\Software\Microsoft\Windows\CurrentVersion\Themes. Set AppsUseLightTheme to 0. |
| Windows Security shows "Unknown" status | Run sc start WinDefend as Admin, then restart. |
Yes, if:
No, if:
Microsoft publishes Insider builds as encrypted UUP (Unified Update Platform) files. The open-source tool UUP Dump converts these to a clean ISO.
Why this method: It’s legal, clean (no malware), and gives you an untouched ISO. | Issue | Solution | | :--- |
Microsoft intended Build 21390 to be part of the Windows 10 "21H2" (November 2021 Update). However, late in development, leadership pivoted to announce Windows 11. Build 21390 became the forking point – the last Windows 10 build before the UI revolution began. This makes it invaluable for developers testing legacy software compatibility.
Microsoft added NVMe power state management and improved ReFS (Resilient File System) deduplication. For gamers and creators, this meant slightly faster load times on high-end NVMe drives.