CVIRT.dll Is Missing From LabWindows™/CVI™

Updated Sep 8, 2020

Reported In


  • LabWindows/CVI 2017 Full
  • LabWindows/CVI

Operating System

  • Windows

Issue Details

I recently upgraded to LabWindows™/CVI™ 2017 or newer for Windows OS. When I open one of my previous projects, I am getting a message that cvirt.dll is missing. 


From the LabWindows™/CVI™ for Windows Version 2017 Readme, you will see that the cvirt.dll was removed. The most common cause of the error is having a project that was built in an older version and recently upgraded to 2017 or newer. Use one of the methods outlined in this document to fix the issue.

Method 1: Install the LabWindows™/CVI™ Runtime (Legacy)
Install the LabWindows™/CVI™ Runtime (Legacy) which you can download from this link. This runtime engine is applicable to the LabWindows™/CVI™ 2017 Shared Runtime or later. This legacy runtime contains the deprecated cvirt.dll which is required for running applications built with LabWindows™/CVI™ older than the 2017 version.

Method 2: Copy the cvirt.dll From Another Computer
If you have an older version of LabWindows™/CVI™ installed in another computer, this DLL will be at the file path C:\Windows\SysWOW64. If you don't have an older version of LabWindows™/CVI™ installed, please contact National Instruments support and reference this article. Once you have a copy of the cvirt.dll please copy the DLL into the following folders:
  1. C:\Windows\System32
  2. ​C:\Windows\SysWOW64
This will allow LabWindows™/CVI™ to locate the dll. Nothing needs to be changed at the registry-level for this to take effect.

Method 3: Update the DLL to the cvirte.dll
To find where your program is using the cvirt.dll and update it to the cvirte.dll, you can use the program Dependencies to locate where it's being called. If you are developing a DLL or updating an old one, use the newer cvirte.dll instead of cvirt to avoid errors like this moving forward. 

Additional Information