When you say you have lost the option to close or minimize mIRC, do you mean that you cannot see the menubar (which has the File, View and other menu items) at the top of the mIRC window? If so, you may be in Full Screen mode. You can move your mouse to the top of the screen and the mIRC menubar will appear. You can then select the View menu and then the Full Screen menu item to exit that mode.