What makes a computer unique?

I was watching some shows on tv about computer thiefs, and they always get busted because every computer has a unique address right? Where is that address located at and why can't the dumb a$$'s change it?

 

There are two unique addresses. First, there is the IP. Which you can see by opening a command line and typing ipconfig. This address is giving to you by your ISP. You cannot change this unless your ISP allows it.

The second address is your MAC address. That address is technically hard coded directly into the NIC. It looks something like 00-26-54-12-DE-FF (type ipconfig /all to see it)and it isn't suppost to be possible to change unless you get a new physical NIC. Now there are ways of changing them, but it doesn't really matter since when tracking someone down you track by the IP, which is tagged to the MAC address.

So basicly, you can change your IP, but even in the event you did, it doesn't matter cause there are logs which show who was using what IP at what time. The only tricky part about tracking someone is getting access to the logs and then actually going through them.