Precision M6400 processor upgrade

I recently bought a precision M6400 from ebay. It was broken - which made it cheap - but I repaired the issues.

I want to upgrade this thing. I used the service tag on the Dell website, and it is out of warranty (of course) which is not an issue, but I reviewed all documentation

for this machine, including the service manual. I have upgraded the video card to the 3700FX from the 2600, which the manual stated it could take. This was true, but the manual didn't state that you would have to change the processor heatsink when you upgrade to this card. :emotion-12:

Then I went to upgrade the ram, again using the service manual - huge mistake. All that did was cause the precision to bark at me. At least the manual told me that it was incompatible memory. Even though, what I purchased was what it stated. So I am still waiting on that to come in. But, in Dell's defense, I didn't purchase anything from them. If I did, I bet it would have worked. But I do not want to spend the amount of money that they charge. And yes, I know You get what you pay for.

I want to upgradde my processor now to the quad core processor that the manual - again states that I can use. But I do not know what I can buy. Will it work with my mainboard? Or do I need to update my mainboard as well, to get it to use the quad core processor. My service tag is <ADMIN NOTE: Service tag removed per privacy policy

I have used CPU-Z to identify my mainboard, and it is dell 0P614F  processor Intel Mobil core 2 Duo T9600 - Q45/43 - Socket P

I did try to goto Intel's website but because my mainboard is an OEM board, there is no help there. So, what processor can I upgrade to? (be specific, if you have an answer please)

Thank you for any help