A generic copy of XP just may work better. I had a problem installing XP when I used a dell disk in a compaq computer. While a had a valid license for the compaq the system wouldn't except it. I had to telephone in to get it activated. It did not stop the disc from loading it just told me that the key was invalid.

Memory sounds like a good place to start. What are you running for clock speeds? Overclocking?
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