Problem with .iso files...

Hi. I know there has to be a way to do what I'm trying to do but I can't figure it out and Google isn't any help either.

I'm trying to create a Knoppix CD (well, I'm trying to build an all in one boot CD with several tools/rescue cds/etc... but that's beside the point). I want to change the background on the desktop when Knoppix first loads up. When I mount the iso to virtual clone drive and try to go in and replace the background file with the one I want (same filename, filetype, image size) it won't let me do it. I'm assuming this is because Virtual Clone Drive mounts the image as read only media or something. No big deal. I copy all files in the iso image to a folder on my desktop, go in, replace the image with the one I want and it works. The problem is, how do I get these files packed back into a single iso with the only difference being the background file that I changed?

 

Have used makelivecd and mylivecd to create updated linux live cds/dvds. There are also trials and freeware windows programs that might do what you want.
http://alexfeinman.com/isorecorder.htm