Network Slow on Domain, Troubleshoot?

For some reason our Internet is really slow on our network. We have about 55 machines, and running SBS 2008. Our network is old (I'm newer here and I didn;t set this up,) everything is badly set up ( there are switches upon switches, upon switches that are not managed,) and there has been switch ports that failed in the past. Half of the switches are in the ceiling (fun stuff). But we are going to rehaul our entire facility in a month or so with new wire and switches etc. in a centralized closet.

But that is besides the point. For some reason right now our Internet bandwidth is much worse than it was about a month ago. We have 12MB Internet.

When I do a speed test I only get about 0.43 on the client machines. When I do it on the server that's plugged into a core switch, it gets close to 10MB. There is no one streaming anything.

Somwhere between here and there, it's getting the life sucked out. To make things more interesting...our wireless Aruba system is also only getting about that same low speed. BUT the AP's and controller are plugged into the core switch...so it doesn't make sense that it's getting that terrible of bandwidth, because the servers plugged into is getting great.


Where do I even start troubleshooting for something like this? Is there some type of network analyzer too or commands? We are going to rehaul the network  here soon, but I would like to put some type of temporary fix on it, so we can at least have subpar bandwidth instead of terrible.