Logic pro 8 & windows (.iso) files

Hi everybody,
My name is Franck and I'm a Logic audio user since 1999.
I made a lot of backups from 1999 to 2005 of logic songs saved under Windows (98 & XP).
I was able to open and convert this files to the Mac Os format with logic express 7, but since I upgraded to Logic pro 8 it isn't possible anymore.
The soft says I have to install the 7 version, but when I try to install the 7 version I have a message "there is an earlyer version of this soft on your computer, do you want to replace it, and then only two buttons : "replace" or "Cancel"! I mean is it impossible to install the 7 version in "parralel" to the 8 version? Is there any plug in or add on who can convert this windows files with the 8 version? Is there any good reason for Logic 8 not opening this files anymore???
I really would like to use my logic backups when ever I want (or need like today!), without having to convert all of them. This is one of the reason I switched to mac os 5 years ago. Thanks for your help!