There are three issues here:
1.) Once something is burned to a CD/DVD is can never be removed unless it is a CD-RW, DVD-RW, or DVD+RW. (Re-writable media.) In that case if you wish to remove the file you must reformat the disk, wiping everything on it, and start over.
2.) You cannot erase single files, modify/update a file, etc on a CD/DVD by normal standards. If you want that ability (enabling you to use the CD/DVD like a floppy, manipulating files at will) you must use special packet-writing software such as DLA or InCD, neither of which are free. The downside, though, is that you must format all disks in advance and there's a greater chance that the disk won't be readable at some later date.
3.) With any CD/DVD, be it -R or -RW, you can normally continue to add files to it (each with a different name) until the disk is full. However, if you 'finalize' the disk you will not be allowed to add anything to it from then on. Finalizing a disk enables it to be used on more players/computers (enhances compatibility) but has an obvious downside. This is a feature that can be controlled in the burning software' options.
All that said, it sounds like you used a CD-R and finalized it, meaning you'd have to throw away the disk and burn a new one. If you have any other questions, note what media you are using (CD/DVD and -R/-RW) as well as what software you are using to burn the disks.
Hope this helps,
I would like to know if anyone could help me with this. I created a MS Powerpoint presentation and wanted to burn it to a cd/dvd. Well, I was successful at burning it only to realize later that I needed to make some changes to the presentation. Now, I've made the changes, but my system will not allow me to burn the updated presentation because it is stating "files can not be copied to this cd because it already contains content, insert new cd". I've tried to save it directly to the cd/dvd drive (D) and it states "file exists and is marked read-only, save the file with another name or location". I'm not sure what to do because the name of the file works for the system of information that is listed on it. How can I save the information on the cd/dvd? Can I clear all current on the cd/dvd? If so, how do I do that? I have searched and could not find anything instructing me on how to do this.