Need advise on monitoring network traffic.

Hi,

I am looking for recommendations for a suitable application for monitoring network traffic.

Some of my users have been complaining the network is slow. My machine is slow when opening mapped network drives and shortcuts to these drives. Once I have accessed these drives they seem to be ok but after periods of inactivity they become slow again. I am connected to a Gigabit switch and have a Broadcom NetXtreme 57xx Gigabit controller.

I also have suspicions a certain individual may be creating network traffic.

I am hoping for a application which is free and easy to use allowing me to monitor the network and traffic from individual machines.

Please advise.

Thanks,

Chris.