No, not all RAM modules (memory chips) are alike, there are roughly eight different types. Obviously, as this is a laptop, this has laptop RAM, reducing it to three options now. To figure out exactly which type of memory you have, use this tool: http://www.cpuid.com/downloads/cpu-z/1.57.1-setup-en.exe After installation of this bit of software, open it (it should have created a desktop icon) and look under the "Memory" tab on the top (arrow 1) and look at what it says next to "Type" (arrow 2)
Now that you have this type, you can ask an employee at your local best buy for this type of laptop memory (DDR, DDR2, DDR3), or look on newegg.com for this type of laptop memory. Make sure that you do not get desktop memory, as this will not fit into your laptop's RAM slots. And you're going to want to look for a 1 gig module for doubling a 512. (the bigger the better, just keep in mind that 1 Gigabyte (GB) = 1024 Megabytes (MB))
I hope this helps!