trying to Identify IP address

I have 20 computers on my network. I have had to track internet usage lately to find abuse. In this process I have pulled up my DHCP table for a list of all the IP addresses on my network. I have found one that I can ping but I don’t know who it belongs too. I have went to each machine on my network and ipcfg’d to get their address but this one is not listed anywhere. I had 4 computers on the DHCP table who’s host name did not register in the table. After going to each machine and entering ipcfg I have identified all the addresses but one. And I cannot find the machine that is logged on to this one address. Is there a way that I can use a command line utility to see who this is? Or is there some process I can use to track this computer?