Basically, the solution you seek, if available, calls for utilization of a number of networking skills. I've had success with identifying the source of an IP address when I had access to a PC on the same subnet. I pinged the broadcast address for the subnet and then used the arp -a command to view the ARP (address resolution protocol) cache to find the MAC address associated with that PC. You can also try using the tracert command as in "tracert 192.168.1.103". Sometimes, if name resolution is available, the tracert command will return a machine name associated with the specified IP address. Of course, if you are attempting to identify a device that is behind some type of NAT (Network Address Translation) the IP address on your side of the NAT device will be different that the one the device is using. I noticed that you said "computer/device". If the address is being used by a router or other non-PC device, you may find success in using the Telnet command and seeing what message the device returns. Some devices such as some routing equipment will return a logon prompt and the name of the device.
Well, the solution is fairly simple. You have an IP, you just don't know what hardware it is associated with. Time to break out NMAP and scan it. If you are not familiar with NMAP, there is a good GUI frontend for it at Source Forge called NMAP Configurator. Anyway, NMAP will give you quite a bit of info about the device if it can find any open ports. If it is a rogue AP, you will find out about it using NMAP. Also, try to telnet to the device. Many routers are configurable through telnet.
It depends on the environment that you're in. Your subject line mentions "internal", but your post doesn't elaborate...I'll assume that you're referring to an internal corporate IP address.
The first place I'd start looking is DHCP logs, if the environment uses DHCP. Then I'd go with "nbtstat -A" to see if I can get some info about the system...like the name. Depending on the environment, the name (due to the corporate naming convention) or a tracert command will give you some information as to where the system itself is located.