It depends on many things.
Generally speaking, yes, you change the entire computer.
Tell me what you have and I can provide a much better answer.
Do you have a laptop or a desktop?
What is the model number and the manufacturer?
Is it a laptop or a desktop?
What is the complete processor model number?
What operating system?
If a desktop, do you know if you have an available PCIe x16 slot?
Provide as much information as you can.
This is your processor: Intel® Core™2 Duo Processor T6600 (2M Cache, 2.20 GHz, 800 MHz FSB) Product Specifications
It is 9 years old.
Actually, I have one with a T7600.
Are you running Windows 7, 8, 8.1, or 10?
And, what model is your dell? Inspiron xxxx , latitude xxxx, etc?
And, how much memory do you have?
At this point, there is not much you can do with such an old laptop except to take it to a recycle facility. Then, get a new laptop.