never, ever have a seen a bad media error. i guess if you put pieces of paper in the drive, you will get that kind of stuff. anyways, MAKE SURE YOUR MEDIA IS RATED 16X before you try and write it at 16x
also, underruns tend to occur from processor heavy applications being run at the same time as a burn. if you just let it burn, you are oftentimes fine.
also part 2, are you running both hard drives on the same ide? or maybe a cdrom and a hard drive on the same cable? tsk tsk, if so