Thank you BOAC.
I think that all these references are for an encrypting/decrypting process and that isn't involved here. The inaccessible files were simply copied from their original locations in 'My Documents' onto the CD - no encryption. When the CD was checked in 'My Computer' on the same machine they were all readable. When the machine was put back to original 'factory' state, attempting to look at the files in 'My Computer' or Windows Explorer produced the 'Data Protection' error message and a blank folder respectively. The right click 'properties' check shows the CD as being full.
There is a Windows function whereby you can disable this 'protection' but doing so for 'Windows Explorer' didn't help.
Aren't computers just wunnerful???
