Repair or Rebuild Microsoft .NET Framework

According to Microsoft, "You can think of the [.NET Framework ] as an agent that manages code at execution time, providing core services such as memory management, thread management, and remoting, while also enforcing strict type safety and other forms of code accuracy that promote security and robustness." This is a fundamental component of Windows and, when necessary, its components must be carefully replaced. 

The .NET technology is evolving and Microsoft has released several interdependent versions and Service Packs for .NET over time. Errors can result when a revision, new version or service pack for .NET fails to install properly as part of routine Windows updates, or when Windows XP is not up-to-date with both Service Pack 3 and .NET framework.

Errors such as 

indicate that one or more of the Microsoft .NET Framework components in the Windows on your computer probably is corrupted or missing. Before following any suggestions on this webpage, see CTI's disclaimer of warranty (below)

If you are using Windows XP, ensure that it is up-to-date (including Service Pack 3). To see which version of Windows and which Windows service pack (SP) is running on your computer, open the Windows Control Panel and select System. The latest installed Service Pack number is listed below the version of Windows. 

To display the Windows Update History on this computer from the Control Panel's System screen:

Look for "Failed" or red X beside any updates that never completed successfully, especially any that include "NET Framework." If your latest update to Windows (any version) included a .NET component, and everything including CTI Navigator was working correctly before this Windows update, try restoring your Windows system files back to the date before the update was installed (see Restore Windows System files in the related articles below), and then update Windows again.  Otherwise, to fix a Microsoft .NET Framework error requires removing/uninstalling the corrupted .NET component and then re-installing it and all of its associated components in the .NET Framework. To accomplish this, Microsoft recommends you use the Microsoft automated .NET Framework repair tool described below. 

Automated Repair of .NET Framework

Microsoft provides a wizard-based .NET Framework Repair Tool that "detects and tries to fix some frequently occurring issues with the setup of or with updates to the Microsoft .NET Framework." To download and run this tool on your computer, click on "Microsoft .NET Framework Repair Tool" and follow Microsoft's instructions. To see more information about this tool, click on "Microsoft .NET Framework Repair Tool Description."  

If Microsoft's automated repair tool fails to fix your error or you are not comfortable running this tool or trying to repair your Windows .NET Framework files yourself (see manual repair below for advanced users), CTI recommends that you have a local computer technician test and repair the Windows .NET Framework in your computer. Otherwise, for free "computer repair, service and support" (such as repairing Windows) Realtor members can contact the http://TechnologyHelpline.com. This tech helpline is funded by your state Association of Realtors as a member benefit and can be reached by phone (Monday - Saturday) at 

Repair Tool Version Note: The current version of the Microsoft's automated repair tool (dated 10-08-2012) supports repairing the .NET Framework 4, .NET 3.5 SP1 (includes .NET 3.0 SP2 and .NET 2.0 SP2) on Windows 7 and earlier (Vista, Server 2008, Server 2003, and XP). 

Compatibility Note: Incorrectly setting CTI Navigator Desktop to run in a "Compatibility Mode" different from the version of Windows in which it is running can cause CTI Navigator to suddenly disappear whenever a CTI Navigator function (such as Login or Send) requests Internet access. To confirm or correct that CTI Navigator is not set to run in Compatibility Mode: open Windows Explorer > browse to C:\Program Files\CTI Navigator [in a 64-bit version of Windows browse to C:\Program Files (x86)\CTI Navigator]) > right-click on CTI Navigator.exe > select Properties > click the Compatibility tab > verify that "Run this program in compatibility mode for" is not checked.

.NET Framework in Windows 8

By default, .NET Framework 4.5 is enabled in a new or clean installation of Windows 8, but .NET 3.5 is not included. The files for .NET 3.5 are available on the Windows 8 installation media as an optional feature. When an app requires .NET Framework 3.5 (or .NET 2.0), Windows 8 should automatically request permission to download the missing files from Windows Update. If this fails, users can enable .NET Framework through the Windows 8 Control Panel or from the system ISO image file. 

To enable .NET Framework 3.5 (and earlier) in Windows 8 Control Panel (if needed by an app):

  1. Open the Control Panel (use the Settings Charm on the Desktop Mode, or type Control Panel on the Tiles mode)
  2. Select Programs and Features
  3. Select "Turn Windows features on or off" (to the left side of the list of installed programs)
  4. Check the box beside .NET Framework 3.5 (which includes .NET 2.0 and 3.0)
  5. Click OK.

To enable .NET Framework 3.5 from a Windows 8 ISO image:

  1. Copy  \sources\sxs\  from the mounted operating system build ISO image to  dotnet35  or similar folder. 
  2. Execute this command using admin privileges:

Note: Copying from the sources\SxS\ folder can be used but is not a Microsoft supported mechanism for normal distribution of .NET Framework 3.5. (see Windows 8 .NET Framework 4.5 is default and .NET Framework 3.5 is optional). 

Manually Repair .NET Framework (advanced users only)

Always try Microsoft's automated repair tool first (see the preceding section). If you are an advanced computer user and Microsoft's automated repair tool fails to resolve the problem, you can attempt to manually repair .NET Framework yourself, contact the state association sponsored technology hotline (see above) for assistance, or have a local computer technician repair it for you. 

To manually repair .NET, follow the steps in the prescribed order for the approach chosen below. Before you start, ensure that your Windows has the latest Service Pack and the latest security patches installed for your version of Windows. (Sometimes Microsoft's latest update includes a hot fix for the problem.) Beware that manual repair may take more than an hour, depending on your computer and which components are damaged or missing.

The sections below represent three approaches to rebuilding Microsoft .NET Framework:

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Standard Manual Repair and Rebuild

To manually repair or rebuild Microsoft .NET, complete the following steps in order as appropriate for your version of Windows:

  1. Verify or create a Restore Point in Windows System Accessories.
  2. Control Panel XP: Add/Remove Programs >
    • .NET 2.0 SP 2 > Support > Repair
    • .NET 3.0 SP 2 > Support > Repair
     Vista/7: Programs and Features > .NET 3.5 SP1 > Change/Remove > Repair.
    If problem is not resolved by an automated repair, proceed with the following steps.
  3. .NET Framework 3.0, and 2.0 are included as part of Windows Vista Operating System; and .NET Framework 3.5, 3.0, and 2.0 are included as part of Windows 7 Operating System. To repair NET Framework 3.5, 3.0, and 2.0 in Windows Vista or 7

1)     Start > All Programs > Accessories

2)     Right-click on Command Prompt > select "Run as Administrator" > Continue

3)     Run "sfc /scannow" to automatically replace incorrect/corrupt versions of system files if possible

4)     If SFC could not fix some files, follow Microsoft's instructions at  

  1. In Windows Explorer, verify or create a C:\Downloads folder (or "C:\Windows\Microsoft.NET\Framework\Downloads")
  2. Download dotNet Fix files appropriate for your version of Windows to your Downloads folder (use links at http://msdn.microsoft.com/en-us/netframework/cc378097.aspx; or go to specific download links below):

1)  Windows XP, 2000, Server 2003:

Warning: The .NET Framework Cleanup Tool should be used with caution. It not only removes the selected version files, hotfixes and service packs to that version, but it also removes files and registry keys shared with other versions of the .NET Framework. All associated versions of .NET Framework must be repaired or re-installed (in numeric sequence) after using the Cleanup Tool. 

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Automated Cleanup of All Versions and Streamlined Re-Install

Use the following procedure if the preceding standard repair and re-build (described above) does not succeed.

  1. Download .NET Framework 1.1   
  2. Download .NET Framework 1.1 SP1   
  3. Download .NET Framework 3.5 SP1 (file name dotNetFx35setup.exe at  http://www.microsoft.com/downloads/details.aspx?FamilyID=ab99342f-5d1a-413d-8319-81da479ab0d7&displaylang=en )
  4. Download the .NET Framework Cleanup Tool (file name dotnetfx_cleanup_tool.zip as above, or see User's Guide and download links at http://blogs.msdn.com/b/astebner/archive/2008/08/28/8904493.aspx )
  5. Unzip dotNetFx_Cleanup_tool.zip (see warning above) 
    • Run dotNetFx_Cleanup_tool.exe
      • In Windows XP, use the Cleanup Tool to Remove All .Net Framework versions (1.0, 1.1, 2.0, 3.0, and 3.5)
      • In Windows Vista, Remove only .NET 3.5 (because earlier versions of .NET are part of the operating system)
  6. Restart Windows
  7. Install .NET Framework 1.1
  8. Install .NET Framework 1.1 SP1
  9. Install .NET Framework 3.5 SP1 
    • Note 1: .NET 3.5 SP1 includes 2.0 SP2 and 3.0 SP2 subcomponents
    • Note 2: This fix does not include .NET 4 
  10. Restart Windows
  11. Install Windows Updates

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Reinstall Only .NET Framework 3.5 SP1 Full Cumulative Update

The .NET Framework 3.5 Service Pack 1 is a full cumulative update that "includes cumulative servicing updates to the .NET Framework 2.0 and .NET Framework 3.0 subcomponents." If .NET was working correctly until recently, you may only need to un-do and reinstall the 3.5 SP1 Update as follows.

  1. Verify or create a Restore Point in Windows System Accessories.
  2. In Windows Explorer, verify or create a C:\Downloads folder (or "C:\Windows\Microsoft.NET\Framework\Downloads").
  3. Download the .NET Framework 3.5 SP1 from Microsoft (file name dotNetFx35setup.exe at http://www.microsoft.com/downloads/details.aspx?FamilyID=ab99342f-5d1a-413d-8319-81da479ab0d7&displaylang=en ) into your Downloads folder
  4. Download the .NET Framework Cleanup Tool (file name dotnetfx_cleanup_tool.zip at http://cid-27e6a35d1a492af7.skydrive.live.com/self.aspx/Blog_Tools/dotnetfx_cleanup_tool.zip or see Cleanup Tool User's Guide and download links at http://blogs.msdn.com/b/astebner/archive/2008/08/28/8904493.aspx) into your Downloads folder
  5. Unzip dotNetFx_Cleanup_tool.zip (see warning above and alternative note below) 
    • Run dotNetFx_Cleanup_tool.exe
    • In Windows XP, use the Cleanup Tool to Remove Only .Net 2.0, 3.0, and 3.5 
    • In Windows Vista, Remove Only .NET 3.5 (because earlier versions of .NET are part of the operating system)
    • Note: An alternative to using the dotNet Cleanup Tool is to uninstall and rename versions 3.5, 3.0 and 2.0 as described in the Standard Manual Repair and Rebuild section above.
  6. Restart Windows
  7. Install .NET Framework 3.5 SP1 (which includes 2.0 SP2 and 3.0 SP2 subcomponents)
  8. Restart Windows
  9. Install Windows Updates. 

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Disclaimer of Warranty. All services are provided under the terms and conditions of CTI's license agreement accompanying CTI Navigator. Assistance in any form is provided only as a convenience to licensed users of CTI products. Problems and solutions may depend on the nature of your system environment and other parameters that are unknown to CTI. By requesting assistance, user agrees that actions and solutions described, suggested or implemented by CTI staff are entirely at the user's own risk and are provided without warranties of any kind. Under no circumstances, including negligence, shall CTI or any of its employees be liable for any direct, indirect, incidental, special, punitive, consequential or other damages, loss, cost or liability whatsoever that result from or are related to use of technical support provided by CTI.


Related articles and Internet links:

Links to Microsoft's Instructions for .NET Framework


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rev.08.12.2013