If you can't locate your computer's model number and you are using a Windows-based system do the following:

Hit Windows key + R to bring up the run dialog box.
In the run dialog box type:

Dxdiag

Hit enter, then You will be prompted with a dialog box asking if it is OK to access the Internet: Hit enter on "Yes". After a few seconds, the "DirectX Diagnostic Tool" dialog box will appear on your screen with information about your computer. Look for the wording "System Model:": that is your computer's model number. or, you can tab and enter on, the Save all information button. There will be a txt file placed on the desktop with all of the information available.