Setting up a modem/router shouldn't require the installation CD. Most of the time that CD contains nothing but the manual (PDF) and other documentation. Your typical modem/router is designed to work out of the box. Just connect the coax cable, plug in your wired devices, establish your wireless connections, and go. And the router's admin page can usually be accessed @ http://192.168.1.1
Of course, you'll eventually want to access the UI to change the default username/password (usually admin/admin), enable wireless security, etc.
But chasing down the CD or its contents from their website is just a waste of time. Not unless you want the manual.