I suggest you use the Microsoft sysinternals such as Process Monitor and Process Explorer:
http://technet.microsoft.com/en-us/sysinternals/bb795533 and perhaps some of their other tools:
http://technet.microsoft.com/en-us/sysinternals/bb795532 It's impossible to say what the traffic is for, if it's incoming connections that are dropped by your computer (or firewall) it's most likely the background noise of the Internet, if it's outgoing connections from your computer it could be traffic related to torrents, Tor, etc.
Use
netstat -nao and the
task manager to identify which pids are doing what as MrTuxracer said. You can enable viewing the PIDs in the Task Manager by opening the View menu, clicking Select Columns, and then ticking PID (Process Identifier) on.
You can also use the console (cmd.exe) with the following command: tasklist
That should keep you busy for a while