imovieHD on a Mac Pro Early 2009

I have a Mac Pro Early 2009 and tried to place my copy of imovieHD on it.
I like the imovie with the timeline more than the NEW imovie. Anyway, my Mac Pro will not let me copy it on to the HD.

I have the imovieHD running on my MacBook Pro 13" with no problem.
My MacBook Pro has OS 10.6.8 on it.

The Mac Pro has 10.7.5

I don't know if that makes a difference.

Thanks.
Brian