Microsoft has acknowledged that its Windows 11 Media Creation Tool is failing to run on some ARM-based PCs after the 25H2 rollout, leaving Arm64 users and device builders with a frustrating roadblock when they try to create installation media directly from an Arm device.
Background
Microsoft ships the Media Creation Tool as an official, supported way to download Windows 11 ISOs and create bootable USB installation media. Historically this tool has been relied on by home users, IT pros, and OEM technicians to build installation media quickly and consistently. The company’s Windows 11 download and support pages explicitly state that the Media Creation Tool is intended for creating x64 installation media; Arm64 ISOs exist, but the tool’s behavior on Arm hosts has now been flagged by Microsoft as problematic.On September 29, 2025 Microsoft updated its Windows 11 25H2 update history and release-health notes to show that the Media Creation Tool (version noted as 26100.6584 in the entry) “might not work as expected on devices with Arm64.” Users launching the tool on affected Arm machines may see the message: “We’re not sure what happened, but we’re unable to run this tool on your PC.” Microsoft confirms the tool currently does not support creating Arm64 media from Arm64 hosts and is investigating.
What exactly is broken — the technical facts
- Symptom: The Media Creation Tool (MCT) exits with a generic failure on Arm64 hosts, often showing the message: “We're not sure what happened, but we're unable to run this tool on your PC.” This occurs when attempting to run the tool on ARM-powered Windows machines or when asking the tool to create Arm64 installation media from that host.
- Tool version called out in Microsoft’s note: 26100.6584 (this number appears in Microsoft’s update history entry describing the issue).
- Scope: Microsoft describes the problem as unlikely to affect most users because running the Media Creation Tool on Arm64 to create Arm64 media is a niche workflow. The tool remains functional for creating x64 media when run from x64 hosts.
- Confirmed workarounds (official): Use an AMD64/x64 host to create Arm64 installation media, or download the Arm64 ISO directly from Microsoft and use third-party USB creation tools to write it to a drive.
Why this matters (practical impact)
For most everyday Windows users the breakage will be invisible: the typical upgrade path (Windows Update or the Installation Assistant run on an x64 device) remains intact. However, the problem is significant in several concrete scenarios:- Device manufacturers and imaging teams who use Arm64 development or test hardware to produce recovery or factory images will be blocked from creating Arm64 USB media on-device.
- Developers and testers who run Windows on Arm for software validation and want a local bootable USB for installs or troubleshooting will lose a convenient, official method.
- Enthusiasts and early adopters who own single-device Arm laptops or tablets and expected to produce media on that same device (for example, to create a recovery USB) will need an alternate machine or process.
- Enterprise imaging workflows that assume on-device creation on Arm machines (rare but not unheard of for mixed-architecture fleets) must be adjusted until Microsoft issues a fix.
What Microsoft and independent sources confirm
Microsoft’s official Windows 11 25H2 update history entry lists the issue explicitly, documents the generic error message, explains the limitation (“The media creation tool doesn't support creating media for use on Arm64 devices” in the current implementation), and says the issue is under investigation. That entry is the canonical, authoritative confirmation.Independent tech outlets and community reporting have reproduced the symptoms and echoed Microsoft’s advice: create Arm64 media from an x64 host or download the Arm64 ISO and write it using third‑party tools like Rufus or Ventoy. Reporting on the RTM and ISO availability also confirms Arm64 ISOs are available for download from Microsoft’s official download site.
Workarounds and recommended procedures (step-by-step)
The immediate practical options to create Arm64 installation media while Microsoft investigates are straightforward and well‑tested. These steps include both GUI and command-line approaches and are geared to different user levels.Quick options (most users)
- Download the Arm64 ISO directly from Microsoft’s Download Windows 11 page (choose the Arm64 edition).
- On an x64 PC, run the Media Creation Tool — it will create x64 media normally; if you need Arm64, use the downloaded Arm64 ISO instead.
Create a bootable Arm64 USB from an ISO (recommended for Arm64 targets)
- On any working PC (x64 preferred), download the Arm64 ISO from Microsoft’s site.
- Use a third‑party USB writer such as Rufus or Ventoy to write the ISO to a USB drive. Rufus supports selecting partition schemes (GPT/UEFI) and appropriate target types; it is widely used for writing Windows ISOs reliably.
- In Rufus (or similar tool) choose: Partition scheme = GPT, Target system = UEFI (non-CSM), File system = NTFS (if required by the ISO), and then write the ISO. Boot the Arm64 device from the USB to install.
For advanced users and IT admins (automation / scripting)
- Use a clean x64 imaging server or VM to mount the Arm64 ISO and apply any preconfiguration or unattended answer files. Keep a canonical, hashed copy of the ISO in your imaging library instead of relying on “on-the-fly” MCT creation. This reduces risk from tool regressions or regional propagation lag.
Verification and technical caveats
- Microsoft’s messaging specifically calls out the Media Creation Tool version associated with the 25H2 servicing baseline and notes that Arm64 hosts are impacted. The update history entry is explicit that the tool’s Arm64 creation from Arm64 hosts is not working as expected. This is a primary, authoritative claim that should be treated as resolved reporting of Microsoft’s own status.
- There can be confusion around build numbers. Community reporting and press outlets reference different build strings (for example, 26100.6584 appears in servicing notes, while some coverage of final RTM ISOs mentions build 26200.6584). These differences are normal during a servicing/enablement cadence (cumulative updates, enablement-package builds, and RTM labels can use different build identifiers). If build identity matters for your deployment, validate the ISO’s winver/build string after booting from media. Do not assume build numbers are interchangeable.
Risks, limitations, and what to watch for
- Single-machine Arm64 users: If you own only an Arm-based PC and have no access to an x64 machine, you may be temporarily unable to produce official boot media on your device. That includes recovery USBs and local reinstalls without external help.
- OEM/recovery scenarios: Some OEM recovery processes expect recovery media produced on the device. If your device shipped with an OEM recovery partition and you’ve wiped it, creating replacement media may require a different host until the tool is fixed.
- False positives and unrelated MCT errors: The Media Creation Tool has historically reported similarly worded error messages for many unrelated conditions (lack of admin privileges, third‑party AV interference, BITS service issues, corrupt temporary workspace, drive problems). If you see the MCT fail on an x64 machine, follow standard troubleshooting steps before assuming this Arm‑specific bug. Microsoft’s own support channels document other MCT error codes and remedies.
- Security posture: Using third‑party tools like Rufus is common and safe when you download software from official project pages and verify checksums for ISOs. Still, adhere to corporate policy in regulated environments — some orgs require only vendor-signed imaging workflows.
Analysis: how Microsoft handled this and what it means
Strengths in Microsoft’s approach:- Microsoft documented the issue clearly on the Windows 11 update history / Release Health page, which provides an authoritative briefing for admins and power users. That transparency lets organizations adjust deployment plans or apply workarounds quickly.
- The problem is narrowly scoped and doesn’t affect the majority of upgrade paths. Microsoft’s staged rollout approach (enablement packages layered on 24H2) reduced the exposure of the issue to mainstream consumers. Community reporting confirms the limited footprint.
- The Media Creation Tool is a long-established “single-click” utility relied upon by many non-expert users. Having a regression that prevents Arm64 hosts from creating Arm64 media — even if niche — breaks a familiar recovery and imaging workflow and creates friction for device owners and imaging teams.
- Microsoft’s advisory leaves no firm ETA for the fix; for administrators who depend on automation and documented SLAs, the lack of a specific timeline is a real operational gap. Until Microsoft publishes a remediation or patch, enterprises should plan conservative pilot deployments and avoid changing production imaging procedures that assume on-device Arm64 media creation.
- This issue is a reminder that even incremental servicing changes can produce targeted regressions in specialized workflows. The fix path is straightforward from a mitigation perspective (use an x64 host or ISO + Rufus), but the user experience hit is real for anyone whose toolchain assumed on-device Arm64 media creation.
- The incident underscores the importance of maintaining alternate imaging workflows, validating canonical ISO images in a controlled repository, and keeping at least one x64 fallback host for emergency recovery tasks.
Checklist: what to do now (concise)
- If you need to create Arm64 media immediately: download the Arm64 ISO from Microsoft and use Rufus/Ventoy on an x64 machine to write a bootable USB.
- If you encountered the MCT error on an x64 machine: verify admin rights, temporarily disable antivirus, ensure Background Intelligent Transfer Service (BITS) and Windows Update services are available, and try again — many MCT failures are environmental.
- If you manage fleets: update imaging runbooks, document the temporary workaround, and keep a validated library of Arm64 ISOs (SHA‑256 hashed). Pilot any 25H2/25H2-sourced images in a representative ring before broad deployment.
- Monitor Microsoft’s Release Health and the Windows 11 update history page for remediation updates; treat any Microsoft “under investigation” note as a signal to delay risky on-device Arm64 media workflows until the fix is validated.
Final verdict
The Media Creation Tool regression for Arm64 hosts is a legitimate, documented issue that Microsoft has confirmed and flagged in its Windows 11 25H2 update history. While the problem is narrow in scope and workarounds exist, it breaks expected workflows for developers, OEMs, and some users who rely on Arm64 devices to produce their own installation media. The pragmatic path forward is to use an x64 host or direct ISO + Rufus-style tooling for now, and to treat Microsoft’s Release Health page as the authoritative place for remediation updates.Be deliberate: verify the build of any ISO you deploy, keep fallback imaging tools and an x64 recovery host available, and avoid last-minute, single-device-only imaging steps during mission-critical maintenance windows until Microsoft confirms a permanent fix.
Source: Neowin Microsoft confirms Windows 11 Media Creation Tool is currently broken for some users