Why is there no increase in memory after the win7 system is added with a memory stick?

I don't know if you have the same problem as me. I added a memory stick to the computer, but the memory has not increased, or it is displayed as the size of the original memory stick. How to solve this problem? Below I will give you the way I solve this problem (my notebook is WIN7 64-bit, originally 2G memory, plus a 2G)

1, I am on a 2GB memory computer Add a 2GB memory stick, which is displayed on the third-party software.

2. Select the right-click property of the computer and enter the computer system interface to display 4GB of memory, but only 2GB is available. Here are some steps to solve this problem.

3. After clicking the Start button, enter ”system“ and search. Once you find the system configuration, click Open.

4. Click "Guide“ and select “Advanced Options” and open.

5. Change the maximum memory to 4096 or turn it off and confirm.

6. Click to shut down or restart to take effect.