Have you tried the instructions given here:
Basically, it involves un-installing .NET Framework Version 1.1 Service pack
1 in Control Panel\Programs and Features.
Then download (a link is on the above KB page), install, and use the Windows
Installer CleanUp Utility, and remove all references to .NET Framework
Version 1.1 Service pack 1 (only!). (A shortcut to the utility will be place
in your Start Menu).
Then reinstall .NET Framework Version 1.1 Service pack 1:
Then run Windows Update again, to install KB929729.
"David Powell" <firstname.lastname@example.org> wrote in message
>I keep getting error code 643 when I am trying to update net framework 1.1,
>is there any workaround for this?