Mac OS X Leopard

General requirements:

A Mac computer with an Intel, PowerPC G5 or PowerPC G4 (867MHz or better) processor

512MB memory
DVD drive for installation
9GB of free disk space
Some features require a compatible Internet service provider, fees may apply.
Some features require Apple’s .Mac service, fees apply.

Feature specific requirements:

Time Machine requires an additional hard drive (sold separately).

Photo Booth requires an iSight camera (built-in or external), USB video class (UVC) camera or FireWire DV camcorder; and an Intel or PowerPC G5 processor. Backdrop effects require an Intel Core Duo or faster processor. Backdrop effects when using a DV camcorder require fixed focus, exposure and white balance.

Boot Camp requires a Mac with an Intel processor and Windows XP Service Pack 2 or Windows Vista (sold separately).

Screen sharing in iChat and in the Finder requires a 128-Kbps Internet connection (300-Kbps recommended).

Front Row requires a Mac with built-in IR and an Apple Remote.

DVD Player requires a 1.6GHz processor or better for improved de-interlacing

iChat requirements:

Audio chats require a microphone and a 56 kbps Internet connection;
Video chats require an iSight camera (built-in or external), USB video class (UVC) camera or FireWire DV camcorder, and 128 kbps upstream and downstream Internet connection.
Photo Booth and Backdrop effects require an Intel Core Duo or faster processor.
Backdrop effects when using a DV camcorder require fixed focus, exposure and white balance.
Some iChat features enjoy better performance and quality with higher system capabilities.
More details

Developer tools require 1GB memory and an additional 3GB of free disk space.