This tutorial will take you every single step of the way through installing Ubuntu 7.04 (Feisty Fawn) using Parallels Desktop 3.0 (Build 4128) for OS X. In other words, even your parents should be able to follow along.
Read it here
This tutorial is for anyone with an Intel based Mac who is curious about Linux – specifically Ubuntu, and has about an hour to kill (not including the time it takes to download Ubuntu).
The steps and screenshots used for this tutorial are specific to Parallels Desktop 3.0 (Build 4128) running on a MacBook Pro w/ OS X (10.4.10). With that said, they will be nearly identical if you have a Mac Pro, Mac Mini, MacBook or any other Intel based Apple Mac.