How do i fix Error Code 0x643 On Window XP .netframework 3.5 fialed update?

How do i fix Error Code 0x643 On Window XP  .netframework 3.5 fialed update?

Question Info

Last updated March 25, 2018 Views 2,348 Applies to:

When installing updates using Windows update or Microsoft Update you may receive Error 0x643 or 0x80070643 (23 Oct-09)


Step #1 => Before doing anything else, write down what .NET Framework versions are currently installed:

How to determine which versions of the .NET Framework are installed and whether service packs have been applied

Step #2 => Now see Resolution Method 2 in this related KB article:

After running the .NET Framework Cleanup Tool (not the Windows Installer Cleanup utility), reinstall all .NET Framework versions (but only the ones you wrote down in #1 above) manually using the download links on the page then run Windows Update manually to install security updates for same.

NB: If you remove .NET Framework 3.5 (SP1) using the tool, reinstalling .NET Framework 3.5 will also install .Net Framework 2.0 SP2 and 3.0 SP2; then Windows Update will offer .NET Framework 3.5 SP1.

IMPORTANT! => If you remove .NET Framework 3.5 (SP1), reinstall your .NET Framework versions in the following order:

    1. .Net Framework 3.5, then...
    2. .Net Framework 1.1, then...
    3. .Net Framework 1.1 SP1

NB: KB923100 references this page:  Please read ALL of it as well as the related page before using the .NET Framework Cleanup Tool.

Step #3 => Check-in at Windows Update and install any critical security updates offered.


Aaron Stebner's WebLog: TurboTax 2009 can fail to install because it thinks the .NET Framework is not installed, even when it is

~Robear Dyer (PA Bear) ~ MS MVP (IE, Mail, Security, Windows & Update Services) since 2002 ~ Disclaimer: MS MVPs neither represent nor work for Microsoft
~Robear Dyer (PA Bear)
Microsoft MVP (Windows Client) since October 2002

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