The message is saying that a TestCompelte process is already open. If another version of TestComplete is open on your system please close it and try again.
Close all the applications that may use the same files that TestComplete uses, for example, web browsers, your tested application, Microsoft Visual Studio, and so on.
Also, check your Task Manager to see if "TestComplete.exe" is running, if so end the task and try again.
https://support.smartbear.com/testcomplete/docs/general-info/installing/installation-steps.html