You have a motherboard that has been designed to use a Merom processor, but you're using a Penryn processor, a T8100. The processor is not compatible to the motherboard. The reason is that your motherboard has been designed to receive processor temperature data from an analogue thermal sensor, but the Penryn processor uses a digital thermal sensor to measure temperatures. Your motherboard is the correct replacement part for your notebook.
You can solve the problem by replacing the processor with a Merom processor. The processor that was in your notebook when it came from the factory, a Core 2 Duo T7250, is such a processor. If you want a more powerful Merom, you could use a T7300. Other processors listed in the T61 Hardware Maintenance Manual are T7500, T7700, and T7800.
If you want to keep the T8100 processor that you use now, i suppose you could replace the motherboard. You would need the version that was designed to use Penryn processors, FRU 42W7875.
Users have reported that it's possible to make the notebook boot despite the error message by pressing the ESC key when the error message is displayed. I have no idea whether the notebook's thermal management will be functional if you do that, and i don't know whether doing it might cause hardware failure. I can't recommend such a workaround.
