I doubt its a dma issue, because I don't think it'd work well up to 15%. I think its more a case of ensuring u have a reasonable amount of freespace on the partition ur burning from and whichever partition is set as the buffer/temporary folder. In addition to that, defrag the hard drive, and in nero do the speed test. Just before u click burn, uncheck burn and check determine maximum speed. Also, go into preferences and do a speedcheck of the various partitions. This will help us determine if its a data throughput problem from the hard drive or only when it gets to the burner.