To install the Flixster desktop player and watch movies offline on your computer, you must have the following:
XP, Vista, 7, or 8
OS 10.6.8 or above (Snow Leopard).
You must also have a 64-bit processor, which is standard on Macs produced after mid-2006. To find out whether you have a 32-bit processor, see this article. Incompatible models are anything with "Intel Core Solo" or "Intel Core Duo" as the Processor Name in the hardware specs. Note that there is also a "Intel Core 2 Duo" that looks similar, but is compatible.
For information about movie playback on iOS devices, please see these articles.