I have a SONY VAIO VGN-NS325J laptop with 3GB RAM. Can I just add a 4GB and have 7GB? Or do I have to have 2 of the same RAM sticks? I have not tried anything yet.
You'll have to find out what type of RAM your laptop supports before trying to install another stick of RAM. If you download CPU-Z and click on the
Memory tab it'll tell you the type of RAM your laptop is using, its
DRAM Frequency (You'll have to multiply it by 2 to get the actually frequency as DDR stands for
Dual Data Rate) and the RAM timings.
The bit you need to be concerned with is the type of RAM (e.g.
DDR3, etc). You'll have to get the supported type. If you buy a 4GB stick of the same type with the same
DRAM Frequency you should be fine. If the frequency and/or timings are different, you may run into problems, leading you to having to go into your BIOS settings and tinkering with the RAM settings. I'm sure you don't want to do this, so it's better if you purchase RAM with properties that match.
Your laptop has two memory slots which can contain a maximum of 4 GB each. You probably have one 2GB and one 1 GB card. Your cheapest option would be to replace the 1 GB with 4 GB.
You can use one of the memory providers' websites to scan your computer and show upgrade options. For example Crucial.
Note that you must be running a 64bit operating system to use more than 4 GB.