If you use Nero CD-DVD Speed, you can check the two discs burnt on the two machines. It will show the difference.

No disc is ever error free, by saying that you have simply proved that you have not checked the disc with the right tools :-)

I have indeed used Nero CD/DVD Speed - exactly as you suggested - and it is reporting no errors on a "Scan Disc" check.

I would also expect that modern hardware and clean discs straight from a sealed packet would be error free - it would be pretty poor if they were always containing errors. As a separate check, I also checked the OEM DVD and it is error free (it was cleaned to ensure no visible dust particles) - on both machines. To check the software is working I used a randomly chosen DVD (Microsoft Flight Sim9) and as I expected, it did show a high percentage of bad sectors, but then it's been in use on and off for three years and it works fine.

All reports by Nero software on the 2008-1 discs are 100% green - no bad or damaged sectors. None of the four DVD drives here will support the "Disc Quality" check so I have run the Scan Disc test alone.

During the writing process - whether making use of Imgburn or DVD Decrypter -, no errors are being reported by either package, no retries are being reported and no verification errors on the 'post write' check, again regardless of package.

Two machines with two different OS and DVD burners are producing the same reports and results but only DVDs burnt on the newer machine actually work in the Mk4 drive.

__________________
Me:
Current: 2011 E71 40D Vermilion Red/Beige Nappa

Wifey:
Current: 2012 R80 Countryman SDX Green/Cream

When i used DVD DECRYPTER even i chose 1x burn speed , the program still burn the DVD at 4x which is the lowest ing speed the disk was disigned and it works. good luck