it's probably just Disc 1
Or maybe it's a joined one.
anyway, i installed 3.80 M33 and i am pleased, here is why:
1- easy to update, all i had to do is copy 3.80 M33 UPDATE folder and copy Sony fw 3.80 inside the same said folder. (this is of course running from 3.52M33-3 or higher)
2- update is now the same as the official one, few clicks and legal crap and you are done.
3- network update is soooo goood, i just updated from 3.80 M33 to revision 2 (3.80-2 M33) with ease, very fast and efficient.