This question is coming from someone completely new to the field, so it may seem obvious/silly to more seasoned professionals. Please be patient with me. 😉
Do you create a new, customized boot disc for every system you are going to inspect, based on what you think you might encounter? Or, do you have one "master" image that you use which contains every driver etc that you think you might need?
Actually none of the above. Typically there is an unknown in every on-site visit so it would be tough to custom build for what I think I am going to examine. So I have accumulated several over the years.
In my case I have a collection of boot disks including Dell workstation and server, HP, Compaq, and Lenovo. I have a couple of disks to examine infected computers. I have disks that load the drivers to interface with my Logicube MD5. I have several versions of unmodified Helix disks. I have BackTrack, Deft and Raptor disks. And I have a couple that I have built following examples in Harlan Carvey's books that include a number of his Perl scripts.
Boot disks are a moving target. Eventually you will end up with a little CD case full of choices.
Not one boot disk does it all. Nearly all of the commercially and freely available disks have everything you need for most systems. I have built a Linux variant boot CD and a Windows boot CD (WinFE), both of which I use more than any others I have only because I've designed them to fit my needs and preferences. It looks much more professional in front of clients to have the desktop of your boot CD customized with your company logo than it does having a cartoon figure.
I may be going out on a limb here with outdated technology…but I also have forensic boot floppies….with Safeback too! I figure, you just never know what you'll come across and keeping a few on hand never hurts.