Overclockin in Windows XP x64

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Just installed Windows XP x64.
In XP 32bit version I had my system @ 3055Mhzs, mems @ 235Mhzs 2-2-2-5, rock stable, running Folding.
Now in x64 version even @ 3Ghzs it gives me a blue screen, MACHINE_CHECK_EXEPTION, and reboots. Second Windows install and still gives me the error.
Anyone with the same problem, or a solution?

EDIT: Tried 2900Mhzs (less 155Mhzs than in 32bit version) still no go, same blue screen =(

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