Double mouse click
The default setting for opening files in the KDE file manager and some other desktop aplication is single mouse click. To get the more familiar Windows like behavior, choose Peripherals in the main Control Center menu, then Mouse. Activate Double-click to open files and folders, (select icons on first click) button. Then click the Apply button. This setting will not influence to Arahne's programs, since they use double mouse click to open files.