Sorry, I don’t have any way to measure the temperature. But so far everything is running fast and with no problems at all, no indication of overheating. It is on 24 hrs a day. The form factor of the motherboard may play some role too. I think Dell is using the BTX for Dimension 9200 and that may help keep things cool. Not sure about Asus.
When you say Nero 7 is dual core aware, what exactly do you mean? The whole suite or the disk burning bit?
Nero vision express v3 (part of Nero 6) is dual core aware. Cannot see any advantage to the ‘burning ROM’ part of the suite using two cores.
If you go to your bios you can see your M/B and Processor runing temps.