sorry, i assume people know everything, (bad habbit),
you need to extract it into a folder and then edit it in the folder, then create a new iso file from the folder,
to do this in Gnome, you would use Archive Manager,
to do this in windows, the easiest way is to copy them off a virtual CD drive or a real cd drive, magic ISO for windows XP is great for this,
then you once you have finished editing the file, in win XP you would put a blank CD in the drive, select all the files in the directory you extracted the iso to, right click and go, write files to CD,
in Gnome you would copy all the files out of the directory you extracted them to and paste them into the CD/DVD creator, which is located in: Places>CD/DVD Creator,
then you would choose write to disk and select your cd-rw drive and write the files,
similarly in XP you would enter your blank cd-r/rw from "My Computer" and write the files to CD, it's been a while since i've used XP so i'm a little rusty, i'm sure you can follow.