Net PCs are based on the Wintel platform, but are configured to be as inexpensive as possible and to discourage users from configuring the machines themselves (the cases also are sealed to discourage users from altering the hardware). Consequently, they have no floppy disk drive or CD-ROM drive. They do have a hard disk though it's meant to be used as a temporary cache to improve performance rather than for permanently storing data. Configuration and management of a Net PC is performed through a network server and Microsoft's Zero Administration Windows (ZAW) system.

Network PC System Design Guidelines
An archived white paper from Microsoft.