how to add files to iso?

How can I add files to an ISO of a live CD?

The problem I ran into is this: Using "Winiso", I tried adding files to a knoppiXMAME livecd iso, by adding files to an already existing folder (roms)...

Now I can't boot off the liveCD of the modified iso, because upon bootup I get the message: "could not find kernel image: KnoppixMAME"

Any help in tracking down the problem in the bootloader, and advice in the correct way to add files to an iso will be appreciated.