eBay long ago took the initiative of writing a DVD Guide, unfortunately finding it hasn't always been easy so here it is...

eBay AU DVD Guide

The only thing that the guide neglects to mention that may be important relates to DVD ROM Drives. Computer DVD drives aren't at all concerned with PAL or NTSC. So even if you don't have the right DVD Player, you can play either PAL or NTSC in a DVD ROM Drive, however most drives only allow the DVD Region to be changed a limited number of times.

In Australia or NZ you will be fine playing any Region 4 (Australian) or Region 0 (Worldwide) PAL -or- NTSC DVD in any Computer equipped with a DVD player.
In the USA you will be fine playing any Region 1 or Region 0 (Worldwide) PAL -or- NTSC DVD in any Computer equipped with a DVD player.
In Europe/UK you will be fine playing any Region 2 or Region 0 (Worldwide) PAL -or- NTSC DVD in any Computer equipped with a DVD player

Best Regards
John
JJA Entertainment