Negative values in the Speed effect won't work on an entire clip; they are intended for changing the direction of playback midway through your clip when keyframing speed effects.
Ah yes forgot about this, thanks for clearing that up! Editing above reply!
I didn't know that hit film had revers effect THANK you Guys for your help ,I was a little surprised that the speed effect wasn't impressive,but still I am very happy with hitfilm 2 ultimate
Yah the speed effect makes it hard to see how much you are actually slowing things down. I frequently have to render multiple times till i have is just right.