Employee monitoring software

Employee monitoring software

We have a conflict at the office between two colleagues. One is accusing the other of surfing the internet most of the day, the other one says that it's not true.

I've tried checking the history file on the computer, but I really can't find a lot of non-work related stuff. But he could be erasing the history of course. 

Can anyone recommend any monitoring software that I can install to check what is true? All computer access the internet through a Small Business Server 2003, the ISA is not active.

Hi to recommend any monitoring software and then maybe point someone to a link for such a program.
I would guess although not mentioned in the forum rules,will be something that we cannot help them with.

My guess is from previous requests for such programs and that request being denied.
[does that make any sense?] 

http://www.techguy.org/rules.html
This may cover it.
Quote.
"Hacking/Interference - This is the deliberate use of any device, software, routine, or activity to achieve or attempt to achieve any interference with the proper operation of the site, as determined by the administration."