Officially, Apple lists the requirements to run the iLife programs like this. First, you need a Mac with a G3, G4, or G5 processor inside. It should have at least 256 megabytes of memory and 4.3 gigabytes of free hard-drive space (if you plan to install all five programs). And it has to be running Mac OS X version 10.3.4 or later. (You also need QuickTime 6.5.2 or later, but it comes with iLife.)
You also need a monitor that can display at least 1024 by 768 pixels. And you can't easily install iLife unless your Mac has a DVD-playing drive.
Some of the programs, however, are more demanding. You can't use GarageBand's built-in instrument sounds, for example, unless your Mac has a G4 or G5 processor. iDVD won't even run unless you have a 733- megahertz G4 chip or something faster, and iMovie requires a 1-gigahertz chip if you want to edit high-definition video.
In the real world, however, savvy Mac fans consider some of those requirements the Computer Jokes of the Day. Thes Apple specs aren't just the minimumsthey're the bare, desperate, stranded-on-a-desert-island minimums.
For example, 256 megabytes isn't nearly enough to get any meaningful work done with GarageBand or iDVD. And running iPhoto on a G3 Mac might be theoretically possible, but it's crushingly slow.
Bottom line: A much more practical minimum for running the iLife programs is a Mac with 512 megabytes of memory (or moremuch more), with at least a G4 processor, running Mac OS X 10.3 and QuickTime 6.5.1 or later.
After that, the only requirement is a creative gene in your body.