To upgrade a processor, it has to be socket, chipset, AND BIOS COMPATIBLE. To determine if it is BIOS compatible, you MUST ask DELL.
However, you can stop now, as your processor is soldered to the motherboard, and cannot be upgraded.
Good advice, thank you! I bet Dell will never tell, because they are more interested to sell a newer model. This kind of upgrade won't benefit them. I will try although.