How to solve the error code 0x800F0906: .NET Framework 3.5 installation error

There are several ways to solve the error code 0x800F0906 when trying to install .NET Framework 3.5. Here are some possible solutions:

1. Use the DISM command: Open Command Prompt as an administrator and type the following command: DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:D:\sources\sxs (replace D:\ with the drive letter of your Windows installation media). This command will enable the .NET Framework 3.5 feature and use the installation media as the source.
2. Use the Windows Update Troubleshooter: Go to Settings > Update & Security > Troubleshoot > Additional troubleshooters > Windows Update > Run the troubleshooter. This will detect and fix any issues with Windows Update that may be preventing the installation of .NET Framework 3.5.
3. Install .NET Framework 3.5 from Programs and Features: Go to Control Panel > Programs and Features > Turn Windows features on or off > Check the box next to .NET Framework 3.5 (includes .NET 2.0 and 3.0) > Click OK. This will install .NET Framework 3.5 from the Windows installation files.
4. Use the .NET Framework Repair Tool: Download and run the .NET Framework Repair Tool from Microsoft's website. This tool can detect and fix issues with .NET Framework installations.
5. Check for antivirus or firewall software: Some antivirus or firewall software may block the installation of .NET Framework 3.5. Try disabling or temporarily uninstalling any such software and then try installing .NET Framework 3.5 again.
6. Perform a clean boot: A clean boot can help identify and resolve software conflicts that may be preventing the installation of .NET Framework 3.5.