I bought a CD-Rom with the Cambridge Advanced learners dictionary, but it doesn't work.Although the software is available for Windows and Mac, it's possible that the system where you've installed it to lacks compatibility with the application. According to the official specs, the software is compatible with Mac OS X 10.4 . It doesn't have support for higher versions since it's not specified. However, you can try re-installing the product or returning it if you are in the 30 days period and obtaining something else compatible with the version of your OSX.
Cambridge Advanced Learner's Dictionary 3rd Edition is a program that offers you clear definitions and prominent guidewords help so you find the meaning you want quickly and easily. It includes maps, illustrations, photos and the 'Let's Talk' section which focuses specifically on spoken English.