Internet connection issues, where is my default gateway?

[Crazy Jarvis]

So my dad's desktop decided to stop connecting to the internet, upon my inspection and investigating ipconfig in the command prompt I noticed the default gateway entry was blank.
ipconfig/release
ipconfig/renew
didn't fix the issue.

Beneath is the data given by the ipconfig/all :

Microsoft Windows XP [Version 5.1.2600]
© Copyright 1985-2001 Microsoft Corp.

C:\Documents and Settings\User>ipconfig/all

Windows IP Configuration

Host Name . . . . . . . . . . . . : computer
Primary Dns Suffix . . . . . . . :
Node Type . . . . . . . . . . . . : Unknown
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No

Ethernet adapter Local Area Connection 2:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : NVIDIA nForce 10/100/1000 Mbps Ether
net
Physical Address. . . . . . . . . : 00-15-F2-89-1A-D6
Dhcp Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Autoconfiguration IP Address. . . : 169.254.222.90
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . :

C:\Documents and Settings\User>
Sorry, I forgot to mention - it is connected via ethernet cable straight into the router.
We have 2 other computers in the household on wireless connectivity which work fine. The router isn't the issue. (We're using a BT homehub)
When putting a wireless modem on the computer it still picks up the connection as before (Limited or no connectivity) but remains Default Gateway-less.
Hi efflandt as said previously with a wireless modem connected (Ruling out the ethernet cable issue) we had the same response from cmd. We have also tried 2 other ethernet cables.
I have since ran some software to reset winsock stuff. That didn't work either, currently running a virus scan and next I'll take down the firewalls and see if they're stopping it connecting.

[MikaSch]

Turn off your modem, then turn off your router (if any) Wait one minute.Turn on the modem first and wait till most of the lights on it get steady. Now turn on the router and wait about 10 seconds and see if you have internet connectivity.

[efflandt]

From that it appears that he is either not connected to a network, or one that is not giving him an automatic IP address. The 169... IP is one that Windows automatically assigns to the interface when it has no IP address, and therefore, no Default Gateway or nameserver(s).

Are you sure that the network cable is securely connected on both ends and not damaged? Or maybe there is some incompatibility between his gigabit nic and an older router, although, if it was working before, that should not be an issue. So the first thing I would try is a different ethernet cable.

Years ago I had a couple of 10/100 ethernet cards that had trouble auto negotiating speed with an old router at times, resulting in 25% or more packet loss, even though the router was capable of 100baseT. Those cards worked fine if forced back to 10baseT (full-duplex worked).