This might be a problem that isn't very intuitive.

When we burn data onto a CD the burning software offers us the option of "Closing the session". If we don't, then more data can be added to that CD. If we do, then no more data can be added.

But one of the effects of not closing the session is that only that PC can read the CD. If you close the session, that makes the CD compatible with other computers. Here's what Mcrosoft says about that;
http://windows.microsoft.com/en-US/windows7/Close-or-finalize-a-CD-or-DVD

I hope that helps.

Mark