Well, I've been able to make bootable CD images using Nero. It includes the boot images for making generic bootable CDs, IIRC. As for making bootable Windows install CD, you need a custom boot image (the one I have is 4KB in size) and a certain specific parameter in the settings, but still can be done with Nero and the information is easily searchable on the internet.
As for the floppy images, I just tend to go to www.bootdisk.com and pick up the ones already downloadable there instead of making my own because the only time I need a floppy image would be a bootable DOS floppy...
Floppy files (.vfd or .fdd) are just direct copies of the floppy, no header or anything. So 1.44MB floppy maps to a 1.44MB FDD file. You need access to an actual floppy drive and a tool to extract the image. On Windows, try WinImage. On Linux, I think dd can do it, but I'm no expert...
