Getting error "Unable to determine the installation folder of TestComplete"

I think you're on to something there, Colin_McCrae.  It's a context thing. If, in a File Explorer window, I double click on a PJS or MDS file, my Windows environment knows that those extensions, when I double click, will automatically run TestComplete and open that file.

I wonder if MSBuild needs something more explicit than just "Run the Project".  Notice the "Executable" field on the screenshot given is blank... that it's trying to run the PJS project but there's no executable mapped in MSBuild to do so.

Something else, based upon the documentation... the MSBuild project has GUIInterative flag set to "True"... this means that it will execute the tests using TestComplete, not TestExecute.  So, it's possible that the machine in question has TestExecute installed... but not TestComplete... in which case, that GUIInteractive flag needs to be set to false. (see https://support.smartbear.com/testcomplete/docs/working-with/integration/with-ms-vs/msbuild.html) Give that a try, RajTC... again, like Colin_McCrae, I'm no MSBuild expert but that seems to be someplace to start.