IMHO, your best bet is still external drives when it comes to music. My personal preference is the new apple airport extreme, and then hang the drives off of it. Serves out your music via network fileshare, then you have whatever music server get it to your listening environment. That way it's not stuck on your old computer when time comes to replace it.
But that said, there are several options for replacing a drive. Norton Ghost is the one I used back when I used windows. Or you can just add the drive internally and not replace it.