[andrewas]

16X DVD driver is worthless if its sharing a channel with an active drive. If that happens, any time the computer wants to read something from the other drive, the IDE interface has to shut down the DVD (and IDE is very inefficient while its doing this), then spin up the other drive, read the data, switch back to DVD which may need spinning up again.

Open up your case and make sure that the DVD drive isnt sharing a cable, if its unavoidable make sure its sharing a cable with a drive that wont be accessed during movie playback. On a standard config that means that it cant share with the drive with the "C" partition. Its usualy safe to share with the CDR, although that will kill your on-the-fly CD-copy rates.