Hi SyedA, Parallels Desktop is a platform on which you can run Windows OS or Mac OS as guest operating system inside a Mac computer. If you have installed Parallels Desktop then you can check whether you are running any guest OS by following methods. 1. Open Parallels Desktop. 2. Click on || on top Mac menu bar > Control center. 3. All guest operating systems installed will be listed in Control Center. Let us know if you have any questions.