Cannot obtain IP address

Good Morning.
I work at a small computer shop, doing repairs mostly.
We have a very basic network, default settings, no security, which we use to test peoples ability to access the internet. It’s a linksys router that we plug peoples computers into.
I have one computer that cannot obtain an ip address. All the other computers plugged into the router get one with no problem. If I unplug this computer, and plug another into the router, it gets one.
The computer is a Dell E510 running Windows XP Media Edition SP2.
Onboard Intel Pro100 nic.
What on this computer can prevent it from obtaining an IP address??