Just get VLC and end of story: it will play most everything you throw at it, be it .avi and .wmv or .ogm (I think it even plays matroska files but I'm not sure). Keep the rest of the players in the rare case you'll find something not playable byt VLC (a full list of what is playable can be found at the the videolan site. Just look around a bit)

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iMac G4 OSX 10.3.9
RAM 256MB
LW 4.10.5 Basic
ADSL anything from 3 to 8Mbps/around 1024kbps

"Raise your can of Beer on high
And seal your fate forever
Our best years have passed us by
The Golden Age Of Leather"
-Blue Öyster Cult-