Many times, hardware (including some webcams) will come with no disk for drivers to install at all. There can be all kinds of reasons for this, but the biggest is, Windows has a (usually) great talent for recognizing and installing hardware with no software needed.
If your web camera didn't come with a software disc, simply plug it in and see what happens. Most often, Windows will recognize it as new hardware and either be able to use it, or guide you through the process of searching for drivers (either online or on your computer) to use it.
Of course, absolutely nothing might happen when you plug it in, in which case you'll probably want to read the instruction manual or visit the manufacturer's website to locate some driver software for the webcam. This is also what you should do if you've lost or thrown away the disc that came with your webcam.