This is due to the way Windows 7 hides taskbar icons that it thinks are not important. Unfortunately there is no way for an application to control how these icons are displayed. You will need to click on the small arrow in the Windows 7 taskbar to see all of the icons that it is hiding from you. You can also right-click on the small arrow in the taskbar to customize the way icons are displayed. I am using the Windows 7 taskbar option "Always show all icons and notifications on the taskbar". The next version of mIRC will actually no longer minimize mIRC to the tray due to this Windows 7 issue.
Do you mean that you are changing the default behavior or that you are going to remove the ability to place mIRC in the tray minimized? Hopefully it's just the former.
