Simply download Something like RivaTuner. (google for it). These let you fiddle with your clockspeeds happily.
Standard 128Mb Pro speeds are 380Mhz VPU & 340Mhz(680DDR) VMEM, and the XT speeds are 412/365(730DDR). Virtually all 9800Pro cards are capable of running at XT speeds on the stock cooling, and most can exceed them. Exactly how much by depends on the card, and whether you install alternative cooling etc.
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Epox 8RDA+ V1.1 w/ Custom NB HS
Summer's here! so ease off the overclock...
XP1700+ @166x12 (~2Ghz), 1.475 Vcore
2x256Mb Corsair PC3200LL 2-2-2-4
Sapphire 9800Pro 400/730