What kind of software do you think is used to make demos,like the once seen in PDC etc by Microsoft or seen on Channel 9.
Example: http://download.microsoft.com/download/c/e/2/ce28874c-4f44-4dbd-babb-727685e2be96/WinFS_IWish_720x486_2mbs.wmv
Basically you have text and sound.
I bet they use Camtasia Studio