Linux: installing packages from a usb (where the OS was installed from)

[Unreliable]

Well, in order to get my [url=http://ubuntuforums.org/showthread.php?t=400236]RT73 Serialmonkey[/url] drivers to install, I need to:

sudo apt-cdrom add
sudo aptitude update
sudo aptitude install build-essential linux-headers-`uname -r`

but since I didn't install linux through the CD, how would I go about installing these modules through a USB drive?

Running Ubuntu, fedora didn't work correctly on startup (3 times tested).