My understanding was from what someone said maybe a year or two ago was that 4.5 is the last DS version that recognizes the old .daz extension and all files saved that way, and that I need to use that to convert all the old .DAZ files to .DUF. However as a link above posted by Razor42 says, there was a problem with all versions before 4.6.2.2(?)with compatibility. So apparently I now need to update to 4.6+ before I can have a program that reliably converts .daz to .duf with no problems.

And since 4.8 does not recognize the old .daz format, everything will need to be converted to a .duf file before I can install 4.8,  open those files & work with the content.