I hope that somebody can help me

I have an Acer Aspire 3003 wlmi notebook with sempron 3000+ processor.
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Mobile Sempron 3000+ 1800 MHz 128 KiB 800 MHz 9x 0.95-1.4 V 62 W July 15, 2005 SMN3000BIX2BX
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Mobile Athlon 64 2800+ 1800 MHz 512 KB 800 MHz 9x 1.20 V 35 W Socket 754 AMD2800BQX4AX
It work when I put it into the notebook but It's getting overheat and froze after 10min of work.
By the bios the cpu is running on 1.4V and I need to reduce it to 1.2V.
Anybody knows in which module is this setting and how to change it?
I'm using phoenix bios editor 2.2.
Thanks
Tibor