Usually it will work, but there's a slight chance that the two sticks don't agree with each other and throw out errors. It's basically a risk you need to decide you want to take or not. RAM kits that come with 2 sticks are tested to make sure the two sticks work fine together, and only then sold together. When you buy two separate sticks, the sticks haven't been tested together, so they might not work well together. But again, like I said, the chances are slim of them not working together. You can usually get the RAM replaced if it doesn't work well.