Network

One of the computers in my LAN is showing full activity (sending and recieveing packets) even when the system is idle. I suspected there is spamming going on and updated my Norton Corporate Edition V 10, and adware personal and ran scans in safemode. No virus was detected apart from a few spywares detected by adware personal. When i restart the machine, immediately it comes on, the LAN shows full connectivity (without blinking) and begins to send and recieve packets. Any idea what i should do?