A friend called the other day. She works at a web development company where most things are done on Windows, but a lonely eMac is kept sitting in a corner to ensure that the sites they produce look good in Mac browsers.

My friend had downloaded a new version of Firefox for OS X and was trying to install it.

“I don’t understand,” she said.

“I’ve downloaded it and got a dmg file on the desktop. I opened that but now I’m really confused.”

What my friend was looking at was this:

firefox-dmg.jpg

For most readers of Mac Devcenter, it’s very obvious what you should do at this point. But to my friend, normally a Windows user who was only paying a flying visit to Mac OS X, it was confusing enough to halt her in her tracks. (Gregory Raiz made a similar point yesterday, detailing his experience of switching to OS X - see his comments about installing apps towards the end of the post.)

I explained what the disk image window was trying to tell her, and everything was fine. But it got me thinking about the design of disk images, and how varied they are.

Many make use of an alias to the user’s own Applications folder, so the app can be installed simply by dragging it on to the alias. This is what happens in the Firefox disk image.

Others are more minimalist. Mostly you’ll see just the app and a read me file; sometimes the disk image window has been designed to provide some degree of instruction. The most helpful I’ve seen recently is that of Hazel:

hazel-dmg.jpg

I love the way the window layout has been designed as a series of steps, each step involving one of the files included in the disk image. Even more impressive is the helpful text at the bottom: “To clean up, eject this disk image and drag it to the trash.” Unnecessary advice for most experienced users, but invaluable help for newbies.

What well-designed disk images have you encountered recently? Or, what clever techniques have you used in any of your own disk images?