Okay I don't know what to say now. Basically I had two problems: the new drive that won't recognizing blanks and Nero that won't burn DL.
In my desperation I reinstalled Windows (was long overdue anyway) and lo and behold, the Verbatim DL blanks are now recognized as such by 4163 (before it was "inaccessible" and "incorrect function").
So problem number one solved. Problem number two: I tried to burn with Nero but it said my data (7 GB) is too big for the 8.5 DVD+R. Tried Power Producer and it burned without any glitch! I have Nero 126.96.36.199, I guess that version cannot burn DL. Which version is everybody using?
I guess now both of my problems are solved and I could burn with my new 4163, yay! Although I'd still like to use Nero in the future, I have come to love it. Nero's just the best. I just have to get the newest version that's all.
To Sen and Kenshin, thanks for trying to help. Really appreciate it