I have 256MB PC3200 DDR SDRAM which im pretty sure is RAM (Im a noob) so I want to put another stick in and have more could I put a 512 stick in with the 256 one and have 768MB of RAM ? Because im thinking of letting my local computer place do it and i want to save some money but i dont want to screw up something while im doing it.

K first of all u need to determine the speed and type of ur old 256 RAM. It can be either DDR or else. As to speed they need to be both the same. Well maybe don't need to but if lets say u got 2 sticks of RAM where one is running at 400 and the other at 200 then after putting them both in they will both run at 200 as it always runs at the slower speed. So the best thing is to have the same type of ram.

with DDR to run at DDR, buy matched sets. Look at your motherboard manual. It will tell you where to put the sticks.

i.e. 2 sticks of 512mb in slots 1 and 3 for example.

PCXXXX = the speed (external speed)

CL = chip latency (internal speed)

Whats the internal speed?

Hmm what brand of motherboard do u got?

internal speed is the speed in which the memory intergrated chips talk to each other commonly known as CL

that is - chip latency

What about external speed?