You can change a computer DVD drive's region encoding a limited number of times. It's much easier than trying to find a new player. Of course, it's on your computer and not in your living room TV. Well, unless you have a Media Center.
To do it:
1.Right click on the drive in My Computer, click 'Properties'.
2.Click the 'Hardware' Tab.
3.Double click on the DVD drive
4.Click on the 'DVD Region' tab and follow the instructions on screen.
I've never tried it, but I'm guessing that the dvd player software doesn't need any changes. I could be wrong though. PAL vs. NTSC comes to mind.
To the person asking how to play region 4 DVD's in the US - easy just go online and buy a DVD player from Australia or a region free player. Region free DVD players can be picked up for $50. Of course our right to buy region free DVD players may soon be gone as we have to comply with US laws on copyright due to the Free Trade Agreement.