A. The icons on the quick launch taskbar (Internet Explorer, Outlook Express, Show Desktop and Channels by default) are all stored in %systemroot%/profiles/<user>/Application Data/Microsoft/Internet Explorer/Quick Launch and to remove/add just add and remove the files from this directory using Explorer.
You can copy any shortcut to this directory and the update will be done straight away, no need to logoff/reboot. As you can see below I have added a shortcut for Word and Frontpage just by copying the shortcut to the Quick Launch directory, easy.
An alternative method is to just drag a shortcut over the Quick Launch bar and it will add the shortcut for you.
All the files in this folder are shortcuts except for Show Desktop and View Channels. See the next FAQ for their contents.