As part of my job when I was younger I installed Office 2000 most days. I remember the progress bar went across the screen about 5-7 times. I think out of this was born what I have termed the Windows XP (or was that Windows 7) ‘snake’. In other words don’t bother showing progress just show a green bar going across the screen and disappearing off to the right continuously until it’s done. I felt that it was kind of an admission from MS that this was better than the progress bar jumping to 99% and staying there for what seemed like forever! This then led onto the Windows Vista / 7 blue circle and now the Windows 8.x / 10 circle of spinning dots. Then you never need to tell the user how long things are going to take!