+1 on John's fine post. I would add:
BACK UP YOUR MUSIC TO AN EXTERNAL HARD DRIVE!!!!!!!!!
I keep a copy of my music on my main computer, on a 750GB USB 2.0 external hard drive, and a third copy on my home file server that has the 1TB drives in a RAID 1 (mirrored) configuration.
When a main hard drive fails, it's a trivial though time comsuming process to restore all my music to an iTunes library. My library of songs (16,000+) is 123GB. Only about 70 songs were prurchased through iTunes or Amazon; the rest I ripped from my CDs.
It will take about 2.5 hours to copy 120GB of music to an external USB 2.0 hard drive depending on the speed of your CPU.
I start my backup at the end of the day when I'm done working and the back up runs while I'm sleeping. In the morning all is well.
My home server is a very modest old AMD CPU 1.8 GHz with 2 GB RAM running Windows Server 2000. It has four 1 TB SATA drives in mirrored pairs. The second pair is a hot back up for the first pair. This means I have FOUR hard drives with my data on it and I can pull any one of them and get the data off it if the server OS hard drive crashes.