There are also two ways you can access your serial numbers in Impulse. Be sure that you are logged into Impulse using the email address you used to place your order.
1) Under the My Games or My Software tab, right-click on the title for which you need your serial number and select "View Registration".
2) Click on the blue question mark in the top-right corner of Impulse and select "Register a product with Impulse..." You can copy the serial number to your clipboard by right-clicking on it.
Note that you will be able to retrieve serial numbers for only those games that require them to run after installation.