Device drivers are added to the kernel. Device drivers are called modules since they are modules of the kernel.
That Trust Cam should already be installed and recognized by the kernel.
You will need software (a program) to use the camera. One of the programs to use the webcam would be Cheese.
As for the modem you have not supplied enough information. You claim it to be a Ralink wireless modem. Without
exact information (Name, Make, model and version number) it is impossible to give anything further that would be