An older program or game asks for the .NET Framework 3.5 before it will run. You agree to download it, and the installation fails. When Windows 10 .NET Framework 3.5 won’t install, the program stays YYPAUS unusable.
Windows 10 includes .NET 3.5 as an optional feature. It is not installed by default, and Windows fetches the files from Windows Update when asked.
Failures usually come from that download step, though a damaged component store can also be responsible.
The request usually appears as a pop-up saying an app on your PC needs the following Windows feature. Selecting “Download and install this feature” starts the process that sometimes fails partway through.
What Might Be Causing It
The feature fails to install for one of these reasons:
- Windows cannot reach Windows Update to download the files.
- The PC is configured to use a company update server.
- The component store is damaged.
- A pending update or restart is blocking feature changes.
Error codes such as 0x800F0906, 0x800F081F, and 0x800F0907 all belong to this family.
First Steps to Try
Try installing through Windows Features.
- Restart the PC to clear any pending changes.
- Type “Turn Windows features on or off” in the search box and open it.
- Tick “.NET Framework 3.5 (includes .NET 2.0 and 3.0)” and select OK.
- Choose “Let Windows Update download the files for you.”
- Wait for the installation to finish and restart.
Make sure the PC is connected to the internet and not on a metered connection during this process.
You can confirm success by reopening the Windows Features window. The .NET Framework 3.5 box should now be filled in, and the program that asked for it should start without the prompt.
If the Problem Continues
Install from a Windows 10 image instead.
- Download the Windows 10 ISO from Microsoft using the Media Creation Tool.
- Right-click the ISO and choose Mount. Note its drive letter, such as E.
- Open Command Prompt as administrator.
- Run DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:E:\sources\sxs, replacing E with your drive letter.
- Restart when it finishes.
This method installs the feature from the local image, without needing Windows Update. If DISM reports a damaged component store, run DISM /Online /Cleanup-Image /RestoreHealth first.
Protect Your Data First
Only download the Windows ISO from Microsoft. Avoid standalone “.NET 3.5 installer” files from third-party sites, which are often outdated or bundled with unwanted software. On a work computer, ask IT before changing update settings.
The Bottom Line
.NET Framework 3.5 is built into Windows 10 but needs its files delivered. If Windows Update cannot supply them, a mounted Windows image and one DISM command will. Older programs should then run normally.
