While viewing the new resultant swf file after converting ppt to swf,you will see a control bar behind the flash like this.
There are some function keys on the bar and I’ll show from left to right.
1.
It means the flash is pausing.If you click it the flash will play and the key will change to 
2.
It means the amount of the slides and which slide is being played. For example,2 of 6 stands for there are 6 slides in the flash and now the second one is played.
3.
Play time.
4.
Of course,it controls the sound.
5.
You can turn off the sound by clicking it.
6.
You can left turn or right turn the slide.
We also can hide the control bar when it blocks the content by the very small triangle which may be ignored in the top right corner.
When conveting ppt to swf,this control bar can help you.