Preventing accidents can be a key part of administrators' jobs. Given that, you might want to hide certain drives from users if they don't absolutely need access.
NT enables you to hide drives from the obvious access points (Explorer and My Computer), although a motivated user could still access them from Start | Run. But you can change that. Follow these steps:
The next time the PC boots up, the computer will hide the drives from casual browsers.
Note: Editing the registry is risky, so be sure you have a verified backup before making any changes.