I'm not sure what you are asking. If you just want to make a bootable CD-ROM, Nero can create a bootable CD directly. Just select "CD-ROM (boot)" when selecting the type of compilation to make. If you want to make a WinImage .ima file, then Nero isn't the tool for you. But an ima file isn't necessary for making bootable CDs.
Here is one link with a bunch of information about bootable CDs that you might find useful: