Uninstalled ADAPTEC DIRECTCD 2.5(96) to correct registry problem. Tried to reinstall. Could not reinstall because DirectCD needed to link to missing cdudf.vxd file. Should have been in my Windows/System/isosubsys file.
Friend emailed it to me as as attachment. Dropped it into the iosubsys file. I shut down and restarted and it is good to go. Have reinstalled DirectCD and it's working.