Is it possible to change the booktype of a DVD+RW to DVD-ROM after the movie has already been written, or do I have to erase and re-write the whole thing again?
I'm using a SOHW-812S with US0J.
You must full erase, then write again.
With Ricoh compatible dvd +rw burners (an Artec for me) you can set booktype to dvd-rom even after dvd+rw is burned. I use dvdinfopro for it.
since an 812 is not a ricoh yes you will need to FULL erase (not quick) to be able to set booktype