Install Windows 11 25H2 on an Unsupported PC

Short answer: You can install Windows 11 25H2 on many PCs that fail the TPM 2.0, CPU-list or Secure Boot checks, using a registry value Microsoft once documented, Rufus’s installer options, or Flyoobe. You cannot get past one hard limit: since 24H2, the processor must support the PopCnt and SSE4.2 instructions. Microsoft does not recommend any of this. It says unsupported PCs are not entitled to updates and are not covered for damage under the manufacturer warranty. Back up first, and decide whether those risks are acceptable before you start.

What Microsoft says about unsupported installs

Read this part before the steps. When you install Windows 11 on hardware below the minimum, setup shows a disclaimer that you must accept. Microsoft publishes its wording:

“If you proceed with installing Windows 11, your PC will no longer be supported and won’t be entitled to receive updates. Damages to your PC due to lack of compatibility aren’t covered under the manufacturer warranty.”

Microsoft also says such devices “aren’t guaranteed to receive updates, including but not limited to security updates,” that a watermark is added to the desktop, and that Settings may show a notice that requirements aren’t met. Its advice is to stay on Windows 10 or roll back to it.

The Go back option under Settings > System > Recovery only works for 10 days after an upgrade. After that, returning to Windows 10 means a clean reinstall.

Check first: you might not need a workaround

Many PCs that PC Health Check rejects are actually capable. TPM 2.0 is often present but switched off in firmware, and Secure Boot often fails only because the PC boots in Legacy/CSM mode. Microsoft documents how to fix both. Try those fixes first. Our guide to each PC Health Check failure walks through them. A PC that passes gets 25H2 the supported way, with no warnings and no watermark.

Limits when you install Windows 11 25H2 on an unsupported PC

PopCnt and SSE4.2. The Rufus FAQ says that if setup reports “This PC’s processor doesn’t support a critical feature (PopCnt)” or “(SSE4.2)”, you cannot install 24H2 or later. That requirement is part of critical Windows code and “cannot be bypassed.” 25H2 shares 24H2’s core, so the same applies.
TPM 1.2 for the registry method. Microsoft’s own wording said the value lets setup skip the TPM 2.0 check, but “at least TPM 1.2 is required.”
64-bit only. Windows 11 requires a compatible 64-bit processor.
Future releases can change. Microsoft can change setup behavior at any time. The Flyoobe developer says the same: newer releases “may introduce requirements that software cannot bypass.”

Step 1: Back up and get the official ISO

Make a full backup of your files to an external drive or cloud storage. A failed upgrade or clean install can erase the disk.
Write down your Wi-Fi password and make sure you know your Windows sign-in password. Microsoft’s rollback steps warn about getting locked out without it.
Download the Windows 11 ISO from Microsoft’s Windows 11 download page, which currently offers version 25H2. Use no other source for the ISO.

Method 1: The registry value Microsoft used to document

From Windows 11’s launch, Microsoft’s “Ways to install Windows 11” support page described a registry value for upgrading from Windows 10 on unsupported hardware. The Internet Archive copy from November 11, 2024 contains it. The current page no longer does (we checked on September 26, 2026), and Notebookcheck reported the removal in February 2025. Microsoft’s instruction read:

Key: HKEY_LOCAL_MACHINE\SYSTEM\Setup\MoSetup
Name: AllowUpgradesWithUnsupportedTPMOrCPU
Type: REG_DWORD
Value: 1

What it did, in Microsoft’s words: it let setup “bypass the check for TPM 2.0 (at least TPM 1.2 is required) and the CPU family and model.” It applied to an upgrade started by running Setup from the installation media while Windows 10 was running.

How to apply it:

Open Command Prompt as administrator.

Run:

reg add HKLM\SYSTEM\Setup\MoSetup /v AllowUpgradesWithUnsupportedTPMOrCPU /t REG_DWORD /d 1 /f

Double-click the downloaded ISO to mount it, then run setup.exe from it.

Limits to know: it does nothing for a missing TPM, only for TPM 1.2. It does not remove the PopCnt/SSE4.2 requirement. Because Microsoft no longer documents it, there is no guarantee current setup still honors it. If setup still blocks you, use one of the methods below.

Microsoft’s registry warning still applies: editing the registry incorrectly can cause serious problems that may require reinstalling Windows.

Method 2: Rufus with the Windows User Experience options (clean install)

Rufus is a free, open-source USB tool from Pete Batard. Its “Windows User Experience” dialog can create Windows 11 install media that skips some setup checks. The developer states that he did not invent these bypasses: Microsoft added them to the installer, and Rufus applies them without modifying Microsoft’s signed binaries.

Download Rufus from rufus.ie or its GitHub releases. The current version is 4.15 (June 30, 2026). The executable is digitally signed and the signature should read “Akeo Consulting”.
Run Rufus on Windows 8 or later. The Rufus FAQ says the bypass options are not offered when Rufus runs on Windows 7.
Insert a USB drive you can erase, select it under Device, then click SELECT and choose the Microsoft ISO.
Click START. The Windows User Experience dialog appears only after you press START.
Tick Remove requirement for 4GB+ RAM, Secure Boot and TPM 2.0. Rufus’s own tooltip says this only bypasses the setup requirements and does not stop Windows from using your hardware.
Optional: Remove requirement for an online Microsoft account, Create a local account with username, Disable data collection, Disable BitLocker automatic device encryption.
Confirm, let Rufus finish, then boot the target PC from the USB drive and install.

This is a clean install: booting from media keeps no files, apps or settings. Restore your data from the backup afterwards.

Method 3: Flyoobe (in-place upgrade from Windows 10)

Flyoobe, formerly Flyby11, is an MIT-licensed tool by Belim (GitHub: builtbybel). Its release notes for version 3.0 describe “the isolated Flyby11 upgrade path for Windows 10 PCs that do not meet every Windows 11 requirement,” with read-only checks for TPM, Secure Boot, memory, architecture, storage and Windows version before the upgrade.

Download FlyoobeApp.zip only from github.com/builtbybel/Flyoobe/releases. The developer warns that flyoobe.com and the GitHub account github.com/flyoobe are not affiliated with the project.
Check the file hash before extracting. For version 3.02.72 (September 23, 2026), GitHub lists SHA-256 ca89995e8945900acb75ceed81d802fb10c707ec213fe6f8877c67c98d30143c. Our Flyoobe safety check shows how to compare it.
Extract the ZIP and run Flyoobe.exe. It needs .NET Framework 4.8.
Open the upgrade path, review the checks it reports and follow its prompts.

We do not give click-by-click steps here. Flyoobe had three releases between September 18 and 23, 2026, and its interface changed in each. Follow the labels in the version you downloaded.

An upgrade keeps files and apps, which is its advantage over Method 2. It also carries old problems forward, and an interrupted upgrade on unsupported hardware is exactly the case Microsoft will not help with. That is why the backup in Step 1 is not optional.

After installation: what to expect

A desktop watermark and a Settings notice that requirements aren’t met, as Microsoft describes.
Updates are not guaranteed. Check Settings > Windows Update regularly and run winver to confirm your version.
Future feature updates may need the same process again, or may not be possible at all.
Version 25H2 Home and Pro end of updates is October 12, 2027. See our 24H2 end-of-support guide for the full date table.

What we will not help with

We do not host Windows ISOs or modified images. Use Microsoft’s download page.
We do not cover activation workarounds. Windows 11 needs a valid license on every PC, supported or not.
We do not recommend unsupported installs on a PC you rely on for work, banking or medical records. If Windows 10 is still an option, Windows 10 ESU gives security updates until October 12, 2027 through a supported route.

Questions

Is this allowed by Microsoft?

Microsoft documented the registry value itself for years and shows a disclaimer you must accept. What you give up, in Microsoft’s words, is support, entitlement to updates and warranty cover for compatibility damage. You still need a valid Windows license.

Will I get security updates?

Microsoft says unsupported devices “aren’t guaranteed to receive updates.” Plan for the possibility that they stop.

My PC has no TPM at all. Which method works?

Not the registry value, which requires at least TPM 1.2. Rufus’s option removes the TPM 2.0 requirement from setup on the media it creates.

Setup says my processor doesn’t support PopCnt or SSE4.2. Can any tool fix that?

No. The Rufus developer states this requirement is part of critical Windows code since 24H2 and cannot be bypassed.

Can I go back to Windows 10?

Within 10 days of an upgrade, via Settings > System > Recovery > Go back. After that, only through a clean install.

Does Rufus’s “Remove requirement” option slow Windows down?

Rufus says the option only bypasses setup checks and does not prevent Windows from using all available hardware.

Why did Microsoft remove the registry instructions?

Microsoft has not published a reason. Its current page only repeats that installing on ineligible hardware isn’t recommended.

Which method should I choose?

Keep your apps and files: try Method 1, then Method 3. Want a fresh start: Method 2. Whichever you choose, fix what firmware can fix first.

Sources

Installing Windows 11 on devices that don’t meet minimum system requirements, Microsoft Support
Ways to install Windows 11 (archived November 11, 2024), Microsoft Support via the Internet Archive
Ways to install Windows 11 (current), Microsoft Support
Microsoft now flags a free Windows 11 system requirements bypass tool as malware, Notebookcheck (February 4, 2025)
Windows 11 requirements, Microsoft Learn
Download Windows 11, Microsoft
Rufus, official site, and Rufus FAQ, GitHub wiki
Rufus 4.15 release, GitHub
Flyoobe repository and README and Flyoobe releases, GitHub

How to Install Windows 11 25H2 on an Unsupported PC