10 minutes?! 
There's definitely not something wrong with it?! Is the 603 really that much slower, MHz for MHz, than the G3? Is it possible to add cache to these machines, as that is said to improve the performance of OS X a lot (I seem to remember reading about some situation whereby the cache can become disabled when putting OS X on a beige G3 and as a result it runs very slowly). A better video card may well help too.
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Main system: custom C2D 2.66GHz tower/4GB RAM/2600XT 512 MB/500GB HD/XP Pro x86+Vista Business x64
Main Mac: Beige G3 minitower (Sonnet G4 500MHz/640 MB DVD/USB/Radeon 32 MB/OS 9.2.2+10.4.11)
There's definitely not something wrong with it?! Is the 603 really that much slower, MHz for MHz, than the G3? Is it possible to add cache to these machines, as that is said to improve the performance of OS X a lot (I seem to remember reading about some situation whereby the cache can become disabled when putting OS X on a beige G3 and as a result it runs very slowly). A better video card may well help too._________________
Main system: custom C2D 2.66GHz tower/4GB RAM/2600XT 512 MB/500GB HD/XP Pro x86+Vista Business x64
Main Mac: Beige G3 minitower (Sonnet G4 500MHz/640 MB DVD/USB/Radeon 32 MB/OS 9.2.2+10.4.11)