Windows Update error 80070643

Windows Update error 80070643 can happen for several reasons. The most common cause is a problem with the .NET Framework installed on the computer. You might also encounter this error when installing updates for Microsoft Office 2003. If you were installing Microsoft Office 2003 updates when you received the error, follow the instructions in the "Microsoft Office 2003" section below. Otherwise, follow the instructions in the "Windows .NET Framework" section.