While there are versions of this model shipping with quad core CPUs, some considerations:
The CPU is soldered to the system board, so the entire mainboard must be replaced to upgrade. This has two ramifications:
1. It's expensive - think upward of 50% of the initial cost of the system, and
2. It voids any warranty remaining on the system.
With anything but the very highest-end notebooks these days, the CPU isn't upgradeable -- except for a very few remaining high-end workstations and gaming notebooks, socketed CPUs that can be upgraded are a thing of the past.
I understand, I have another Inspiron bought in 2009 and then I thought it could also substitute in the new models.
Thanks for your answer