Windows
If you do not see the Mozy icon down in the system tray on your machine by the time and date, the easiest way to tell if Mozy is installed is to go to Start > All Programs in Windows and see if you have a listing for MozyHome or MozyPro.
If it is, it is and you can then go to MozyHome/MozyPro > MozyHome/MozyPro Status to put the icon back down in the System tray.
If it is not there, it is not installed. See: How do I install Mozy?
Mac
If you do not see the Mozy icon in the upper menu bar, the easiest way to find if Mozy is installed on your machine is to click on the Apple icon in the upper left corner of the screen and go to System Preferences and see if Mozy is listed there.
If it is there, you can go into the Mozy Preferences and select the setting to Show status icon in menu bar.
If it is not there, it is not installed. See: How do I install Mozy?