KMPlayer will play back the video nicely at slower or faster speeds u can change video speed up and down 5% at a time, i cant remember the default settings but hit F2, Audio Processing,Basic Audio Filters click the 2 check boxes "Enable time stretching" and "Use previous method"
Enable Pitch Scaling will just make it sound how WMP or VLC does at different speeds, chipmunk ect probably not what u want
Anyway i just mentioned this if u wanted to play around a bit and test different speeds till someone answers you