The FAQ quotes postet by Doc Caliban above: I do not understand a word of it.
Anyhow, I can report that I installed the Purevideo thing. Mainly because I wanted a cooler CPU when playing DVD's, with less fan noise. I got a new taskbar icon with lots of new settings, so obviously the installation went well. I used WMP10 for this to work. In the Purevideo settings "Hardware acceleration" was on as default, and it made me feel very optimistic at first. However, I could detect no difference at all, with the different settings. Same amount of CPU usage. Same fan noise. Same picture quality, as far as I could see. Uninstalled.
(Something is essentially wrong with DVD playback on the 9300, in my opinion. One thing is the Purecrap thing and the appearent need for specialized knowledge to be able to read the different FAQ's and stuff. But for me it is the noise, mainly. Then the fan noise is only the smaller part. The noise and vibration from the drive itself is worse. It sometimes makes makes the whole table shake and tremble! My first laptop with DVD was a Toshiba Tecra 266Mhz with hw decoder, bought in 1998: It still runs exemplary: Completely quiet, cool, smooth etc. Same thing with even the cheapest stand-alone players I have seen, costing less than the ram chip of the Dell).