I think your best course of action would be to download the standalone version and try that... If all else fails, reformat and then apply the SP1 update as soon as you've installed the os( again via the standalone version as this causes less problems over the long run ). This is the optimum way to apply the service pack.

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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::SAMSUNG WRITEMASTER DVD-RW/PIONEER DVD::HIPER MODULAR 530W PSU::THERMALTAKE ARMOUR Jr CASE::RAZER COPPERHEAD MOUSE::VISTA HOME PREMIUM SP1