Internet tracking and monitoring: Recomendations Please

Hello, I have a client (business with 5 networked PCs) that wants to monitor internet use; what sites visited and time on. It is a small business on a small budget. All employees will know this is being done. I need an easy to use program with good tech support. What is out there, what have you used and what do you recomend? THANKS for your feedback.
Brian Adams
Practical Solutions
N. Georgia