I wanted to create a file copy program in which progress bar indicates progress. Now if I started n copy/paste operations, that many progress bars should be displayed like windows 8 does. 
The program should be like one window, say "SHOW", is displaying QProgressbar for copy/paste of 1st operation. When 2 copy/paste will start before 1st one finishes, the 2nd QProgressbar will be added in SHOW and hence there will be 2 progressbars in SHOW.
Well create a layout (a vertical layout i suppose) and then create as many QProgressbar you need and add them to your layout with addWidget and that's it.
If you need scrolling, try using a QScrollArea.
How to add new QProgressbar to an existing window?