Add all the files as usual, remember to put the boot catalog file (in this example, "multicat.bin") and your boot disk images.

To ensure maximum compatibility with IDE CD-ROMs, you should choose "Fastest Priority" for the boot catalog file and boot disk images.

Highlight these files and right click, select "Change Priority":



Choose "Fastest Access":



On the CD Layout Properties menu, you need NOT to check the "Bootable" checkbox:



Make sure everything is okay and then you can create ISO image:



Remember to choose "ISO Image File":



The ISO file will then be created.