Question : Network/Bandwidth monitoring tool for non-server (multiple routers & VoIP)

I have downloaded many trials but all the ones that I have tried so far only monitor my computer.  We are in a small office environment without a server or a domain server.

Does anyone know of a good product that will monitor the bandwidth on my entire network?
We have been experiencing some VoIP phone issues and I want to check on the bandwidth that the company as a whole is using.

I'm not sure if this information is necessary, but thought I would include it?
5 static IPs > 2 go to wireless routers & 3 go to VoIP equipment
Mostly Vista Business machines & at least XP Pro, about 10-15 total
My machine is Vista Business x86

The main line that comes in from Verizon goes into a 8-port switch that then goes to the 2 wireless routers and 3 pieces of the phone system.
We have had some issues about the routers hogging up the bandwidth leaving our phone system with issues of cutting out.

Thanks!

Answer : Network/Bandwidth monitoring tool for non-server (multiple routers & VoIP)

There are a number of good products.  If you're looking at a comprehensive bandwidth monitoring programme without going into the complexity of netflow analysis, have a look at Cacti (http://www.cacti.net) for starters.