You can keep 'writing files' to non-rewritable cd's right up until the cd is full to capacity. So if after the first time you write files to that cd - and you don't use all the space you can go back later and add more files.

What you cannot do is delete those files and add more.

As for why you cannot access those files from another computer, perhaps that pc doesn't have a program to run the recently added file?

Even though this is a dated thread, perhaps somebody can benefit from my input.

Try to remember back when Compact Discs first became something that could be applied and gernally used by the average home computer / PC users. This was sometime around the mid 90s when the second edition of Win95 was releasing. For all intents and purposes, all CDs available at this time were effectively non-rewritable, or in other words, what the CD had on it when you first got it was all that it would ever have on it, even if it had un-used space, there were no easily usable tools available to the home user to burn more information onto this extra space. It would still be a few years from this time before an add-on technology came along.... like CD Burners for the home enthusiast, and the software packages that were came available (Nero, just to name one) to allow the home user to make/copy/burn their own CDs.

There are four basic operations in play with these first-gen CDs that effectively made them non-rewritable: 1) the software used to originally write/master the CD; 2) the chemicals and materials used to construct the CD media; 3) the lasers inside the CD drives used to read information off the CD; 4) the corresponding drivers running on the computer that allowed the computer to recognize the CD Drive and read properly read data from it (whether it was data data like numbers and words, or audio data, or video data, whatever). There are many many variables involved with these 4 basic operations, but there are a few that come to mind that may have been involved with the problem originally reported here - a file burned onto a cd of one computer could be read from that computer but not from another computer. I have seen this problem many times, both with data CDs, as well as audio CDs, and I've seen it with CDs burned/mastered by computer companies as well as those burned by home enthusiasts. Before CD burning was released to the general public, it was a lot easier for the computer industry to maintain standards among themselves governing the adoption and use of related standards such as Red Book, Blue Book, Yellow Book, ISO, Joliet, etc. Same basic scenario was in play pre 1983 when one company controlled the entire telephone network in the u.S, but after the break-up, many people at home first getting accustomed to and acquainted with the situation of buying, installing and using home telphones soon discovered that all telephones and telephone standards are not equal nor applied equally and universally.... like grandpas pacemaker going on the fritz every time the cordless rings...... or my aunt, who's computer-controlled doorbell ding-donged each time her neighbor's automatic garage door was engaged.

Short answer - that file that you burnt to a CD on one computer and can read from that computer but not other computers, may have been unknowingly burned to include conform to one or more standards or conventions of CD-burning-formats that may not be universally known by, or recognized, or not setup to work on the other computers..... in a VHS, Beta, Super Beta kinda way.