The only time I ever got the "Delayed Write Failed" messages in Windows was when there was a hardware problem with the disk drive.

I don't know how to get rid of the messages or turn off write caching (have you tried going into the device manager? There's a write-caching checkbox for hard disks, perhaps there's one for optical drives), but I think the root of the problem is that it's simply a bad drive and needs to be replaced.