This is what apple has done to people Anyways go get the following programs, it isn't overclocking btw. All it is, is saying that your motherboard can support those ram speeds. However you do not want ram that runs at 1.65volts though I do not know much about ram timings on laptops. 1333mhz should be good.
use hwinfo32, pcwizard, cpuid to get info of your current ram.
If you want to use your current ram then yov will need ram of same speed and timing (size can vary).
But if you want to get the fastest ram that your board can support then you will need to dump your previous ram (if they are not identical in timing and speed)
post some specification of your hardware so we can guide you more to buy the fastest and best ram (use cpuid)
also to use 4gb or more ram you will need a 64bit window
as 32bit window can support upto 4gb only
If my above plan sounds good, here are 2 options at newegg. one has a case latency of 11, and is on sale for $34.99 and the other has a case latency of 9 and is on sale for 60.99. Both are for 8GB sets.