Your operating software may be the same as Vista since it hints at current user cannot write to disc.  I would google your software with that statement and see how its overcomed.  It appears that you must be an administrator instead of a common user to load it or you have some sort of user account control that needs to be turned off similiar to Windows. 

No, if Carrara 7 pro isn't going to load, Carrara 8 Pro would not either.  You could also go to DAZ and see how they load Carrara 8 pro to Mac; Carrara 7 Pro should load the same way.  Jan