If the progress of Windows Upgrade Assistant is stuck at 99% for more than four hours, here's something you can try. Note: Make sure you follow these steps before you restart your PC. Otherwise, the Media folder might be unavailable.
Open File Explorer, type C:\$GetCurrent, and then press Enter.
- Copy and paste the Media folder to the desktop. If you don't see the folder, select View and make sure the check box next to Hidden items is selected.
Restart your PC, open File Explorer, type C:\$GetCurrent in the address bar, and then press Enter.
Copy and paste the Media folder from the desktop to C:\$GetCurrent.
- Open the Media folder and double-click Setup.
Follow the instructions to start the upgrade. On the Get important updates screen, select Not right now, and then select Next.
- Follow the instructions to finish upgrading to Windows 10. After you're done, make sure to install available updates. Select the Start button, and then select Settings > Update & Security > Windows Update > Check for updates.