Installing imovieHD 6 onto a Mac Pro (early 2009)

Hello-

I have a MacPro tower OS 10.7.5 and want to install imovie HD onto it.
I get and error and it won't let me.
Is this because the OS is too new?


I have the imovie HD working fine on my macbook with OS 10.6.8 running on it. Should I downgrade the Lion on my MacPro to Snow Leopard?

Thanks.