A file required to install an optional feature could not be downloaded.
I am not receiving the source code during installation of .NET Framework 3.5.
Check whether it is a work/school PC and whether a proxy is used.
If it is checked and resolved from above, you do not need to proceed to the next step.
I am not receiving the source code during installation of .NET Framework 3.5.
Difficulty Easy · Estimated time 5 minutes
Check points: Record the error code, when it occurred, and any recent changes.
A file required to install an optional feature could not be downloaded.
Difficulty Moderate · Estimated time 10~30 minutes
Check points: Make sure the feature is enabled and reflected in the Windows features list.
If “computer slows down” repeatedly, it is better to narrow it down to excessive background processes and insufficient storage space rather than changing several settings at once. First look for CPU, memory, and disk bottlenecks in Task Manager and check startup programs, storage space, and temperature.
Among boot problems, the “powers on but does not boot” symptom may be related to boot file corruption or storage device issues. Distinguish between the POST stage and the Windows startup stage, then check in that order: external device, boot settings, and recovery environment.
Content review date: 2026-10-07