OK. I have a -DS3P with Q6600 that I just turned on. I'll wait afew minutes
Now, you say the fan doesn't come on - at all? Or only after a few seconds?
I have tried to duplicate the problem - no luck.
The only time I saw something similar was when I was setting up to OC. A few times, the system would lock up and reboot. Then it would re-reboot (?) back to normal settings. Is your system doing something like this?