If you just got it, the two driver letters sounds about right. Windows 7 is going to let you open either "drive" and explore the contents. If it doesn't, leave the reader plugged in, and reboot the computer.
You will need to create an Adobe account for the DRM, or log in to your existing account if you have one. You will also need to get the
Sony Reader Library (click that link to get to a downloadpage) and authorize the computer and 950 to a Sony Reader Store account. After that, you can sync between the store on your computer and the store on your reader, and either use Reader Library to manage your books, or use other software if you prefer.