Sorry, no idea. I just googled "flac", & the pages I found said that Nero needs some sort of plug-in to burn them. Had a quick look, but not yet found where to get one.
---------- Post added at 18:49 ---------- Previous post was at 18:47 ----------
A ha.
http://www.bitburners.com/Nero_Audio_Plugins_by_MauSau/
http://www.bitburners.com/Software/D...Audio_Plugins/