How To Monitor Bandwidth (40 - 50 Systems)

I show up at this business. They have about 40-50 systems. They have a 2003 AD server with a router, and 4 switches. There is also a dvr system on the network for cameras.Each switch is daisy chained together. Everything is working correctly except for the fact that the network drops about 5 times a day. Before they called us, they would just unhook one switch and plug it back in and it would work.At first, we took that switch and exchanged it with another switch in a computer lab to see if just the computer lab goes down. If it did, then that switch was bad. That wasn't the case, the whole network still went down.We had already left, but when we go back, our first choice will to see if there is a loop anywhere within the switch that will flood the network. Then, we were going to see if there was a switch that was getting a lot of traffic on the network to try to track it down.