If you installed the Facebook Browser application on your computer, you should be able to find it under Start > Programs (All Programs; depending on your OS). However, if you can't find the application on the mentioned location, the default path where all programs are being installed on your Windows based PC is C:\Program Files\Nameofthe_application. It's advised to look in this location also in order to find any installed programs. If you changed the location of the program during the installation process, you should check the other location for the executable file.
