Sorry for the delay in posting folks!
I have a temporary solution which works for me:
Go to Liggy-Dee’s site, and download Optiarc 7170 v1.04 firmware as suggester by Ed01 (Thanks mate!) and flash your drive. Take a backup of your present firmware first, though.
From what I observed,
It now reads and writes CDs,
it writes all DVDs quite well, except there is a 5-8 second delay before it starts. I have tried only Nero though, so it might me a problem with my comp. I’m gonna do a fresh install and let you ppl know.
for the reading part, It now reads the DVD-Rs it could not before. It can now read the DVDs it writes too. HOWEVER, there are still some DVD-Rs with me that windows does not read, but ISOBuster does.
So, as a solution, I would recommend that firmware, and use ISOBuster in case of any troubles.
This drive sounds quite buggy, and there’s even a sticky about similar problems with other NEC/Optiarc drives. So, I’m gonna get this replaced soon, after my exams get over.