If you have the .NET Framework installed on your PC you may have received update KB953297 (Microsoft .NET Framework 1.1 Service Pack 1 dated October 13, 2009). In a number of cases this update installation fails with an error code of 0x643 or 0x64c. This requires the user to remove all of the components of the .NET Framework already installed and reinstall the components. Microsoft has issued an Article ID 953297 that describes known issues with installing the update. Known issues refers to Article ID 923100 that provides specific steps for removing and reinstalling the software. Method 2 in that article provides a link to software written by Aaron Stebner that will remove all traces of the .NET Framework if method 1 fails. Expect to spend at least an hour removing and reinstalling software although method 2 can speed up the removal process drastically.