User interface preferences can be different for each user of your computer.
Linux primary OS:
Parallels Workstation for Linux allows user to select preferable font, its size and other parameters to be used in system dialogs. Click Browse button near Dialog font field and choose new font if you wish to.
To restore the default font and its size use the Default font button.
To disable tooltips deselect Show tooltips checkbox which is selected by default.
The Help Browser Executable field shows the path to an executable file of web browser used for displaying help for Parallels Workstation. By default help is displayed in Mozilla web browser. If it is not installed on your computer or you prefer another browser, locate its executable file using browse button.
Windows and Linux primary OSes:
If the Parallels Workstation wants to attract user's attention to an operation that is going to be performed or to some situation, it displays a message that contains a description and a Do not show this message again checkbox. If you select this checkbox, in the same situation the message would not be displayed. Restore hidden messages button on this tab allows to reactivate all suppressed messages.
The system does not allow to suppress messages reporting potentially dangerous situations.
The appearance of the User Interface tab in Linux primary OS:

The appearance of the User Interface tab in Windows primary OS:
