If you click the system menu button in the top left hand corner of a window ie. the button you usually double-click to close a window, it will popup the usual system menu but with a few added functions (these vary depending on the type of window).
This allows you to select a background picture for a window. You can choose to have the picture displayed in various ways, eg. tiled, centered, etc.
Note: Displaying a background picture slows down the display of text in a window significantly.
If beeping is turned on, mIRC will beep any time a message is sent to the window if it is not active. This setting is remembered across sessions for each window.
You can clear the text in the current window buffer or you can save the text to a file.
This allows you to position a window outside of the main mIRC window and onto the desktop.
This option is available in channel windows and allows you to create a second editbox, for general use. You can press Alt+Q to show/hide the editbox. Also see a related option in the Other dialog.
This appears in Channel windows, it allows you to set display settings for events for a specific channel. The default display settings for all channels can be set via the IRC dialog.
If flashing is turned on, the mIRC window/icon is flashed if there is a new message in the window while mIRC is not the active application. The flash sound specified in the Event Beeps section is also played.
This allows you to change the default font for a window. The font settings for each window will be remembered across sessions.
If logging is turned on, any text displayed in a window will be logged to a file. This setting stays on across sessions until you switch it off. The filename is automatically taken from the name of the window.
This option is available in channel windows and allows you to change the position of the nicknames listbox.
You can tell mIRC to remember or forget the position/size of a window. If you select remember, the next time that window opens up it will do so in the saved position. If you choose reset, the window will be moved back to its previously saved position.
Note: If a window's saved position lies outside the size of the main window then it will open in a default position and size. To force a window to open up in default positions assigned by windows, select forget.
This option is only available in custom picture windows, it allows you to save the current picture to a .bmp file.
This allows you to set the line-spacing for messages in a window.
This appears only when a window is opened in Desktop mode and forces the window to stay above all other windows.
This turns timestamping of events on/off for a window.
This appears in Channel/Query windows, if turned on, mIRC auto-opens websites as they are mentioned in a message.