Have you tried installing SP1 using a 'standalone' copy? Thats what I used and most others in this forum. I'm not sure how your getting the updates as SP1 isn't officially released yet. If you could explain where your getting the copy from or what type it is I/we may be able to help you more...

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AMD X2 BLACK EDITION 3.2GHz SAMURAI COOLER::GA-M51 MB-HEATPIPE CHIPSET COOLER::3GB XMS2 PC6400 RAM::GEFORCE 8800 GTS 320MB 575/900MHz::160GB BARRACUDA RAID 0::SOUNDBLASTER AUDIGY::LITE-ON DVD RAMDRIVE/PIONEER DVD::HIPER MODULAR 530W PSU::THERMALTAKE ARMOUR Jr CASE::RAZER COPPERHEAD MOUSE::VISTA HOME PREMIUM SP1