For who uses the MSN toolbar, if you would you like to know the mechanism of how the bar provides the functionality to open new tabs within the same IE window browser. Just try to switch between the tabs and notice the taskbar downward, you will notice that a new window was activated and the current been hidden. If you concentrate and think more you will realize that the toolbar is passing arguments contains the window Number and the group of windows it interacts with. So this means that the tool bar is doing the same as you are opening a new window otherwise what Mozilla Firefox does which switch between the tabs by creating an instance of a new browser component included within the same Window Browser MDI. Since this Functionality is added to new Internet Explorer 7 which expect to release with the shipment of Windows Vista to be involved into the new OS.