You can certainly continue using your PreSonus AudioBox even if you no longer have the CD.
The "AudioBox 1.2 CD" that may have been included with your device is a driver installation CD. While the 1.2 driver may work for your computer, ideally you want to be on the latest driver for your computer's operating system (e.g. Windows 7, Windows 8, etc).
Visiting the website for the latest driver versions of your PreSonus hardware is always recommended.
As of March 15th, 2015 the v1.3 driver is the most recent driver for those running Windows 7+.
If you are using a Mac then, as indicated on the AudioBox downloads page, you do not need to download any drivers. The AudioBox USB will work as class compliant, meaning you only need to connect it by USB for it to sync properly with your Mac computer (OSX 10.4+).