Unable to install .net 4 code error: 66A Windows encountered an unknown error RRS feed


  • Hello,

    Here is an article offers useful tips on installtions of .net framework you can refer to:

    If this issue still exists, What is your OS? If it is Vista or later, follow the two setps shown below and try reinstalling to see if the issue is fixed.

    1. Verify that if you have turned on the feature of .NET Framework.
        (Control Panel - Programs and Features - Turn Windows features on or off - Verify that the box next to Microsoft .NET Framework has been checked)

    2. Use Verification Tool to verify .Net Framework has been installed well on your OS. If .Net Framework cannot be verified on your computer, you can try to follow the steps mentioned in this blog to repair the .NET Framework.

    If the installation still fails, I think we need to collect the logs for further troubleshooting. After collecting logs, you may send file to me (

    The steps to collect the log:
    - Try to clean your "%temp%" folder (Start Menu >> Run >> Type "%temp%")
    - Install VS.
    - Collect the logs from "%temp%" folder
       Collect tool:

    Please remember to mark the replies as answers if they help and unmark them if they provide no help
    Monday, November 8, 2010 6:01 AM