User Identification

Hi,
I have a process or an user NPIF37169 (I am not sure) in my NT for the last couple of days.It takes a DYNAMIC IP address from my DHCP. I am trying to find the user/computer of it. I know the IP address and the Unique Identifier for it. But when I check in my network (about 60 computers) I dont find any computer using that IP address or the NIC address. Is it a process within the NT taking an IP or is it someone entering my system? How do I find it?
Any help to ascertain the cause is most appreciated.

TIA
K.S.Vijayabaskar
Singapore.