When I installed it on my G4 desktop, things went smoothly. I already had iTunes 4.6, so it skipped over that. On my laptop, though, I experienced a hard freeze: the computer completely locked up during the installation process and had to be hard rebooted. Luckily, it started up fine, and when I retried the installation, it went off without a second freeze. I was even being good and had all the other software shut down and wasn’t messing with the laptop while the installation was taking place like I sometimes do. So, do remember the other golden rule: back up and be careful when installing new software!