Installing After Effects 7.0 on OSX 10.7.5

Hi,

I've been trying to install my old copy of AE on my new iMac 3.4GHz i7, 20GB RAM with OSX 10.7.5, but I keep getting an error message stating that the launcher program can't open because PowerPC is not supported anymore.

Is there a way I can get the install to work, or will I have to buy a new version of AE?

Thanks!