Were these disks created on a Mac? There have always been incompatibilities between Windows PCs and Apple computers. I have never been able to exchange any data between the two.
It sounds like yes, the CD's were burned on a Mac improperly. I'd advise the Mac user to utilize a proper burning software (like Toast) if they plan on sharing files with Windows users.
And Pat, what have you been trying to share between platforms? I share files constantly with no problems (accept the occasional font issue).
Don't worry; it has been years ago since I tried that last time. Maybe things have gotten better by now, but if I can avoid it. I will try to do so...