Got Error 643 when installing .NET Framework

I tried installing an update for the .NET Framework 1.1 with my Vista when I got this error message, see below. I also received an error code 643. I have seen the Microsoft websites but I need a simpler or easier method to resolve my problem.
Experts, please help me!
Windows Update
Some updates were not installed
Succeeded: 1 update
Failed: 1 update View missing updates
Error (s) found:
Code 643 Windows Update encountered an unknown error,
Get help with this error
