I\'m using a progress bar to show the user how far along the process is. It has 17 steps, and it can take anywhere from ~5 seconds to two or three minutes depending on the weath
Vista introduced an animation effect when updating the progress bar - it tries to smoothly scroll from the previous position to the newly-set position, which creates a nasty time lag in the update of the control. The lag is most noticeable when you jump a progress bar in large increments, say from 25% to 50% in one jump.
As another poster pointed out, you can disable the Vista theme for the progress bar and it will then mimic the behavior of XP progress bars.
I have found another workaround: if you set the progress bar backwards, it will immediately paint to this location. So, if you want to jump from 25% to 50%, you would use the (admittedly hackish) logic:
progressbar.Value = 50;
progressbar.Value = 49;
progressbar.Value = 50;
I know, I know - it's a silly hack - but it does work!