Open questions are: 1, 2, 7. For 2: yes, I have an old dual CPU (each single core) motherboard as my client PC (running Vista 32). But I didn't give any thread limitations and I was talking about the official client, not about any miner. So the question remains why it's using CPU at all.

And if I understood you correctly, it's not worth running *any* mining software on the server (although the server is running anyway), because the miner would increase CPU usage causing more electricity costs not worth the results. Correct?