What are the model specifications on your current processor? You can check the socket of the compare those specs with those Intel® Core™2 Quad Processor Q9400S against what you have as a starting/reference point.
Most likely, but still possibly not. The motherboard may not support the specific processor, but it is worth a try. The socket is the same. But you may need to install a new heatsink for the new CPU. It has a higher Thermal Design Power.
Check this link if you need help installing a CPU:
3 
2
the intel processor is 2.66 ghz / 6m /1333 /05A.core 2 quad core
Aeryn TwoFeathers 의
What are the model specifications on your current processor? You can check the socket of the compare those specs with those Intel® Core™2 Quad Processor Q9400S against what you have as a starting/reference point.
Abdur Rahman 의
Most likely, but still possibly not. The motherboard may not support the specific processor, but it is worth a try. The socket is the same. But you may need to install a new heatsink for the new CPU. It has a higher Thermal Design Power.
Check this link if you need help installing a CPU:
HP rp5700 Repair Central Processing Unit(CPU) Replacement
Nikhil Shah 의