Well I have searched for this on the net...and here's what I found
<1>
Simulation of Overwriting(in Nero CD/DVD Speed) and
Actual overwriting are different ballgame alltogether
<2> Most of the people who have successfully overburned did it with DVD+R
[though DVD-R has somewhat greater capacity than a DVD+R]
<3> Plextor DVD writers seem less prone to Overburning failure
<4> Verbatim seems to the brand of choice for overburning though it can also be done with cheap media (apna MoserBaer is also not doing bad in the international arena

)
<5> And finally though I have enabled overburning [under Nero "Expert" tab under "Option"] to 4600MB (this is the max. that Nero lets you, however this size can be increased with a Registry hack), yet when I try to burn even 4500MB I get an Error "Could not initiate Disk-At-Once" after which the DVD is ejected ...so again I am asking for anybody who has
ACTUALLY overburned DVD-R in Nero...how did you do it ?
Currently I am trying with ImgBurn...will let you know if its successful with overburning
P.S. I use BENQ-DW1650 with a firmware version BCDC...will it be helpful if I upgrade it to BCHC
