|What would be the purpose of the upgrade?|
If it's just for better overall performance, it would be better to install more memory. If gaming is what you're after, the bottleneck is the weak Intel GMA X3100 graphics. A CPU or RAM upgrade can't overcome that.
The link below lists a few laptops in the C700 series. Assuming your laptop uses the same motherboard, it appears the Intel Pentium Dual Core T2310, Pentium Dual Core T2330 & Pentium Dual Core T2370 are possibilities. There are probably others as well. You'll have to do some research. Hopefully you realize that laptop CPUs aren't cheap. You're looking at well over $100 plus you still need more memory.