Corrupted DVD data discs of large audio files

Hello, I have XP, 1 gig ram, 2.650 gig hz, NTI-DVD-Maker. Wave files were recorded with Sound Forge & stored on 150 & 250 gig hard drives. The data mode for coping the files with NTI was used to archive 8-10 files per DVD disc. NTI software said that coping process was satisfactory, no errors. Upon trying to replay the files on Sound Forge, I got corrupted files msg for some of the files on most discs, ouch (hundreds of discs).
Now, the 708 starts burning CDs or DVDs & stops with mechanical error msg. I first thought the problem was NTI, but after reading your website problems I am very suspicous of the 708 which I thought was functioning flawlessly!!