Using Roxio Creator LE Dell Edition Download : 2.4.32a - Problem with file copy pdf & XL

I am using Roxio Creator LE Dell Edition Download : 2.4.32a to make DVDs of important project files ( mostly Word, with pdf pictures and drawings and several XL files)

I am suddenly finding (with XP on Inspiron 9300) difficulty in copying readable files onto DVD disk. Seems no problem with Word. This is particularly with .pdf files but also some XL files. I am copying several sub folders (3 or 4 levels down) . I got over it for some key pdf drawing files by copying  the sub folders (which contained the individual files) direct to the disk. However for some files it really has to be to copy as folder/subfolder/maybe even a further subfolder to make sure that the disk is in some order and not cover with hundreds of single files with no particular order.

The final disk is ony 75% full

The error comes when you try to open some (not all!!!!) of the pdf/XL files from the disk, in Adobe reader or fro Xl

Any ideas? Will buying a later version or a completely different copying program help? Or is it something more basic.

I need to make professionla, well structured disks. Any practical advice very welcome

stiggersdc