I'm a bit of a newcomer to Mac's and I need some suggestions on how to upgrade my Imac to 10.4.3 Tiger. My sister bought a single licence Tiger upgrade. She installed it on her laptop. She sent me the Tiger DVD but my Imac only had CD/RWcd. Apple support will send me a CD version if I send back the DVD version but that leaves my sister without her disk as a backup. anyone have any suggestions? Thanks mucho.