When you try to install an update for the .NET Framework 1.0, 1.1, 2.0, 3.0, or 3.5, you may receive Windows Update error code "0x643" or Windows Installer error code "1603"

To resolve this problem, you must fix the MSI software update registration corruption issues, or uninstall multiple versions of the .NET Framework by using the .NET Framework Cleanup Tool, and then reinstall those components.

To troubleshoot this problem, follow these steps starting with Method 1. Proceed to the Method 2 if Method 1 does not resolve the problem.

Method 1: Fix MSI software update registration corruption issues

For more information about how to fix MSI software update registration corruption issues, click the following article number to view the article in the Microsoft Knowledge Base:
To fix this problem automatically, click the Fix it button or link in the 971187 article.


Then visit the Windows Update Web site and try to install the updates:
If the problem is not resolved, proceed to Method 2.

Method 2: Repair the .NET Framework

To repair the .NET Framework, you must uninstall multiple versions of the .NET Framework by using the .NET Framework Cleanup Tool, and then reinstall the components.


To do this, follow these steps:

1. Click the following link to download the .NET Framework Cleanup Tool:
   
   http://blogs.msdn.com/b/astebner/archive/2008/08/28/8904493.aspx
2. Use the .NET Framework Cleanup Tool to uninstall the .NET Framework versions 1.0, 1.1, 2.0, 3.0, and 3.5
   
   Note The cleanup tool does not let you remove the .NET Framework 2.0 in Windows Vista or later versions because the .NET Framework is installed as an operating system component.
3. Restart the computer.
4. Download and install the following components:
   
   • .Net Framework 1.1
     
     http://www.microsoft.com/download/details.aspx?displaylang=en&FamilyID=262d25e3-f589-4842-8157-034d1e7cf3a3
   • .Net Framework 1.1 SP1
     
     http://www.microsoft.com/download/details.aspx?familyid=A8F5654F-088E-40B2-BBDB-A83353618B38&displaylang=en
   • .NET Framework 3.5 SP1
     Note This will also install .Net Framework 2.0 SP2 and .Net Framework 3.0 SP2
     
     http://www.microsoft.com/download/details.aspx?familyid=AB99342F-5D1A-413D-8319-81DA479AB0D7&displaylang=en
5. Restart the computer.
6. Visit the Windows Update Web site and install the updates:
   
   http://update.microsoft.com