Originally Posted by Mr. H
As noted by live4ever, perian should solve your .avi playback problem.
In addition, you really wouldn't regret adding 512 MB RAM to your computer. If you can stretch to getting two 512 MB sticks, great, but don't worry about that too much. 10.3.9 runs fantastic on 768 MB RAM.
If you add more RAM to your G5, they must be in pairs, so adding 512 MB means adding 2 x 256 MB sticks.
With the price of RAM these days, it's not usually that much more expensive to go for 2 x 512 MB sticks.
As well, only add guaranteed RAM, as G5s are very fussy about RAM quality. In the States I believe Crucial RAM comes highly recommended.
Do you have a 4 or 8 socket G5?http://tinyurl.com/3cbmt3