That's because they're not there.
You need a third party tool like Radclocker that will add an overclocking tab to the driver interface.
Also, you need a 9500 PRO that is 'unlocked'. Sapphire 9500 pros are unlocked, but lots of other ones arent, and if it's locked you'll have to flash the videocard's BIOS with a Warp11 bios in order to overclock it.
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Radeon 9500 (hardmodded to PRO, o/c to 322/322)
AMD AthlonXP 2400+ (o/c to 2600+ with 143 fsb)
3dMark03: 4055