The best way is to Copy the Runtime Folder from Poser 7 (if you have it the Program Folder) to a new Folder (such as Poser 7 Content) located in a Data Folder, such as the Documents or Public Shared Folder. Then launch Poser 8 and Add the new location as a Runtime. Do the same for your Download: Runtime if you have any content installed there.

ratscloset
aka John