Most computers do not have floppy drives these days, but there are still lots of diagnostic and rescue tools supplied in floppy disk format. For example, hard drive manufacturers have diagnostic programs that you need to run and mail them the output before you return a faulty drive. While some of these are also available as CD or USB stick images, not all are and you still end up with a collection of odd tools on different media.
The Ultimate Boot CD contains well over 100 floppy disk images, tied together with a boot menu so you can run any of them from the same CD. The collection is wide ranging and includes CPU and RAM testing tools, hardware identification, system information, benchmarks, BIOS tools, hard disk diagnostics and management software, hard disk erasure and cloning programs, partitioners, boot managers, file and filesystem tools, network tools and various Linux and DOS boot disks.
Placing them all on one CD means not only can almost any computer boot from them, but they are all in the same place. The CD also includes a program to make a copy of itself on a USB stick, so you can even use it on computers without CD drives, like netbooks.
These are all boot disks, they are totally independent of the operating system installed on the computer, and they contain tools for all operating systems.