Error 0x80073712 trying to install NET Framework 3.5

Hello. The error 0x80073712 usually means some system files needed for installing .NET Framework 3.5 are either missing or damaged. This prevents Windows from finishing the setup properly.

Just to confirm, how exactly are you trying to install it? Are you using the "Turn Windows features on or off" option, or a different method like a standalone installer or command line?

For now, try this first step to check and repair Windows’ core files:

1. Right-click the Start button → choose Command Prompt (Admin) or Windows PowerShell (Admin)
2. Type the following command and press Enter:

      dism /online /cleanup-image /restorehealth
   

This will scan your system for any corruption in the Windows servicing components (the part responsible for optional feature installs like .NET) and automatically repair any damage it finds. Once that completes, you can try installing .NET 3.5 again.

Let me know what happens after you try this.

Hello,

Download Windows 10 ISO file and mount it to DVD drive..

Go to sources/sxs folder. Copy sxs folder to C:/Temp.

Next, run this command:

dism.exe /online /enable-feature /featurename:NetFX3 /All /Source:c:\temp\sxs /LimitAccess

Once command executed successfully, .NET framework 3.5 will be enabled.

For detailed steps, you can refer:

https://www.kapilarya.com/how-to-enable-net-framework-3-5-on-windows-10

Let us know if this helps!

Note: Included link in this reply refers to blog post by a trusted Microsoft MVP.