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OSX 10.3 should run on it ok if you max the ram out.

Still quite a useful web and email mac. Just don't run more than one app at a time on it or it will grind down to a halt.
 
Run 10.3.9 on it and it can handle the internet OK. Use it to run classic mode as well for any old apps you have that are still useful, as this mode has been abandoned on the new machines.
 
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