It may be correct, but it depends on how many devices are plugged in.
You have two IDE channels each one has Device0 (master) and Device1(slave), so you can plug in four devices. First channel and Device0 will be, most likely, your hard drive, unless it is SATA.
Are all four channels occupied?
Sorry. I re red the first post. You are talking about external drive, that one is USB not IDE.
When you burn, does it burn whole file on DVD.
If the file is 700 MB, you will see only about 30% of DVD burned. If you burn it on CD it should be almost full.