B-locker is a simple, inexpensive and yet complete time management
solution for renting computer time. It is primarily intended for
Internet Cafes.
It doesn't mandate you a billing system. Whether you use an automated
billing system or just accept cash personally, B-locker only manages
time that you were paid for.
The "death" timer allows use of client computer only the time that you
set. Once the time is over the mouse and keyboard are blocked and the
computer can't be used.
No reboot of client workstation is needed. It's that simple!
Give it a try:
http://stargazer.110mb.com/b-locker/