Why My PC can't be upgraded to Windows 11 25H2

Flyby11 (created by developer builtbybel) is currently one of the easiest tools to bypass these restrictions because it automates the "Server Setup" trick, which skips CPU and TPM checks during the upgrade process.

Before starting, there is one hard requirement that cannot be bypassed, even by Flyby11. Your CPU must support the POPCNT (Population Count) instruction.

If your CPU is older than 2008 (e.g., Core 2 Duo), you cannot install Windows 11 24H2 or 25H2. The system will simply not boot.

Most users are safe: If your PC was made after 2010, you are likely fine.

To upgrade Windows 11 to 25H2 on an unsupported PC:

Step 1: Open the extracted folder and double-click Flyby11.exe. You may need to accept a security warning (SmartScreen) by clicking "More info" > "Run anyway.

Step 2: In the tool, look for the option to Download Windows 11 ISO.

Step 3: Once the ISO is mounted, Flyby11 will show you different methods to install.

Step 4: Click to run the method. A standard Windows Setup window will appear (it might look like the Windows Server setup—this is normal).

Step 5: Proceed through the screens.

Step 6: Click Install. The PC will restart several times. The process will take 30–60 minutes.

Currently, this is one of the best for upgrading Windows 11 23H2/24H2 to Windows 11 25H2.