play one downloaded song first to see if download complete

you c drive has enough space.  But could be the songs downloaded incomplete. verify that first.  If the songs are good, you might want to reinstall nero. 

(although the number of songs on your target cd is the same of that in your source, there may be no content being written; check the sizes).

nero verifying step does not change anything; it just verifies content against source and give you a status.