I agree... (the only thing close to similar behaviour was the old 'Blaster' worm, but that would shutdown XP every 60seconds...)...
I'd check all the cables inside the PC Case, ensure the HeatSinkFan is properly seated... Motherboard health and temps.
Please post your computer specifications.
--- 0wN3D by 3gG ---
Here are the specs
Vista Home Premium
Intel (R) cpu 2160 @ 1.80 GHz
Ram 2021 MB
32 Bit OS
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