i rememebr asking that in a thread a few weeks back..maybe two or three..was adviced..and i religiously took that advice.. to keep the last previous exe file.. as well as the original. just in case. 

so..right now..i'll burn onto a rewriteable dvd.. the original bryce pro..the one i bought, the last update before this one, and then this one. same goes for the content. since it's re-writeable, i'll delete any other versions that exist. 

as for the installing..uninstalling bit.. when you install this version..and it asks for whether it should uninstall the previous version..let it do it. you'll have a clean bryce without doubles of anything. As long as you do the above stuff first. So incase anything goes wrong.. you at least have the previous version to fall back on. 

the only hitch i keep getting? you know when you add things to the content library? obps, mats, sky lab etc? how do i deal with that not getting completely erased when i install the content bit?