When installing Windows, especially from a USB drive or DVD/CD, failing at 99% completion can be frustrating. Here are some steps to troubleshoot and potentially resolve the issue:

Step-by-Step Troubleshooting Guide:

• Check the installation media: Ensure you’re using an official Microsoft CD/DVD or USB flash drive from a reputable source.

• Restart your computer: Sometimes, simply restarting can resolve the issue. Try to restart your computer and then retry the installation process.

• Reinstall the operating system: If none of the above steps work, try reinstalling Windows from a different USB stick or CD/DVD.

• Run the System File Checker (SFC) scan: Open Command Prompt as an administrator and type:

   sfc /scannow

Follow the on-screen instructions to run the scan.

• Check for corrupted files: Run the DISM scan using:

   dism /online /cleanup-image /restorehealth

• Disable and re-enable the installation: Disable the installation, then enable it again:

1. Press F8 during startup to disable the operating system.

2. Press Ctrl+Shift+Esc to open Task Manager.

3. Find “Startup” in the Processes tab and click on the Windows Boot Process.

4. Check the Startup tab under “Windows Activation Services.”

5. Right-click on it and select “Disable”.

• Run the DISM repair tool: Open Command Prompt as an administrator:

   dism /online /repairhealth

• Check for registry changes: Open Regedit to view or modify Windows Registry settings.

• Reinstall Windows: If you’re using a USB drive, try reinstalling Windows from that stick.

• Contact Microsoft support: Reach out to Microsoft Support for assistance if none of the above steps work.

Additional Tips:

• Make sure your computer is connected to the internet before attempting to install Windows.

• Use a wired Ethernet connection instead of Wi-Fi for the installation process.

• If you’re installing from a USB drive, ensure it’s not a corrupt or damaged device.

• Keep in mind that if you have a previous version of Windows installed, you might not be able to upgrade directly.