This is taken from the D-Tools forums:
Daemon Tools v4 will support Windows XP x64. That basically means that it has to be rewritten from scratch. DT uses a driver that's deeply anchored in the system, which is necessary for being able to fool copy protections. This takes a very long time. It's not just a simple printer driver, emulating copy protections is a very, very complex task, please don't forget that!
As of today version 4 is still not released.
Brian