Totally agree. Backing up is not longer an option nowadays. It's a definite necessity. However, software registration is usually not a problem if not much hardware is changed. Windows and the usual software apps we use are quite benign. But some VSTis/softsamplers need re-registration even when we change our HD. Any small component in the PC is changed, the registration process needs to be renewed. That means a few extra days in getting a new key depending on which part of the world and which time zone the developer is located. But I agree. The best software I spent on is Acronis TrueImage which saves me hours of headaches.
Anyway, audio tracks are always better to be stored in a separate dedicated HD, be it a PC or a notebook. I would never put the audio recording drive the same as windows. You want the HD to spin fast and not hindered by any other background software that may use the HD. So for a notebook, a firewire or USB2,0 drive is a definite must.
Partitioning is easy nowadays with XP. Not like the days of old when we need to run fdisk etc.
As for registry cleaners, you'll be surprised how much a good one can make a difference in stability of the system. After a clean install of a new OS, my registry cleaner picks up a few hundred errors. Everytime my windows is updated, errors will appear in the registry. When I install Microsoft Office for the first time, my registry had 300-400 additional errors. It helps to keep my registry clean and my system run smooth and fast. But beware of bad cleaners - some kills the registry instead (especially from Norton, I've heard) by removing wrong stuffs. RegSupreme is one of the safer ones.
As for HD breaking down, don't you just hate it when they do that after the warranty expires? I agree with you. That's why I've given up on SCSIs. Expensive and they die anyway after some time! But my backup is in HD (external) which I don't use at all - hopefully it doesn't die without any warning. Perhaps I should follow you in backing up in DVD-Rs.