One of the key functions of DVD Studio Pro is the ability to convert to MPEG2. Unfortunately when you upgrade to Quicktime 6, that ability is lost. Doesn't matter if you even install over a Quicktime 6 Pro serial number DVD Studio Pro still won't have the convert to Quicktime 6 functionality. From what I can see Apple is selling MPEG2 for Quicktime 6 on their store for $20. It should be included if you purchased DVD Studio Pro after Quicktime 6 was released.