Generally you can install Debian from a cdisk or a mounted ISO image , but if you do not have a CD driver, installing Debian via the network may be a good choice. I assume you want to install it from Windows. It is simple.
Just download win32-loader here:
And run it. Go ahead, and the loader will download the necessary files. Finished, reboot your compuer.
Choose Install Debian on the Windows boot menu. Then the installing interface which shows on the screen is familiar to us. Just make sure the computer can connect to the Internet. You can both let it get the network configure automatically or set it yourself.
Tip: back up your data before the operation.