The CPU is the main - most expensive chip in your computer. You shouldnt change it without vast knowledge of computers. As the symptoms you describe could be a caused from a number of problems, I personally beleive it would be plain stupid to waste money on the most expensive part of your pc, when in actuality the fault could be one burnt out wire. As Mick_f said, if it is under warranty, don't change a thing, and contact the retailer you purchased the PC from.

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