you welcome , btw incase it wasnt obvious i meant you should check with cpu-z if you have some free ram slots , seems your current ddr2 ram is pc4200 , anyway it will not give you any speed boost whatsoever for two reasons:
a) theres a direct connection between the processor bus speed to the ram ,the ram must be at same bus speed of the processor cuz if it will be lower , well so will the processor speed , for example if the processor bus speed is 200 and you got ddr1 400 which runs at a 200mhz clock that fits fine but if lets say you'd replace it with ddr1 pc4200 which runs at 266mhz clock you wouldnt gain any performance boost why? cuz the processor got everything to do with it the ram can never run at a higher clock speed then the processor bus , so in this scenrio the only way to fully utilize the pc4200 ram to its max or at least close to it is to overclock the processor then its bus will go up.. and so will the ram clock speed.. , btw the processor bus and its speed (mhz) are two diffrent things , the total mhz is determined by a hardcoded number within the processor (called multiplier) double the original bus speed for example if the multiplier is 9 and the bus is 200 then 9x200=1800mhz or 1.8ghz
b) when you have 2 diffrent types of ram , the "faster" one will automatically be downclocked to the same speed as the "slower" one , they simply cannot run together at diffrent speeds , and as alredy said on a..
you should just buy same type of ram you alredy got , preferably with same timings to avoid conflicts , also to be on the safe side better check on the ram/laptop manufacturer sites that the specific ram your gonna buy was tested 100% working with your laptop , see just cuz you buy a ram that your laptop/motherboard should support it doesnt mean it will like it