First, you want to lock down your systems using the group policy editor gpedit.msc. This will allow you to limit what non-privileged users can do to your systems. You should read up on system policies.
In order to restart your systems remotely, use the following command (start a cmd window first) : shutdown -I. This will allow you to select a system and shut it down or reboot it.
If this sounds complicated, you may want to have a look at Windows
SteadyState[
^], which is very helpful in an Internet Cafe setting.
Unfortunately, there is no version for Windows 7
But Vb.Net and keyboard hooks are not suitable to control your computers.