I ran into this problem a couple of times on XP systems. The ethernet card fails to get an IP address from the DHCP server. Even a new ethernet card fails to get an address. This could indicate a problem with the winsock.

This method seems to work. If possible, test if you have winsock corruption by running the netdiag tool. You probably don’t have it installed so you have to get it from the XP CD.

1. Insert your Windows XP Setup CD, and then locate the Support\Tools folder.
2. Double-click the Setup.exe file.
3. Follow the steps on the screen until you reach the Select An Installation Type screen.
4. On the Select An Installation Type screen, click Complete, and then click Next.

When the installation is complete, follow these steps:

1. Click Start, click Run, type Command, and then click OK.
2. Type netdiag /test:winsock, and then press ENTER.

Reinstall Winsock.

Step 1: Delete the corrupted registry keys

1. Click Start, and then click Run.
2. In the Open box, type regedit, and then click OK.
3. In Registry Editor, locate the following keys, right-click each key, and then click Delete:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Winsock
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Winsock2
4. When you are prompted to confirm the deletion, click Yes.
Note Restart the computer after you delete the Winsock keys. Doing so causes the Windows XP operating system to create new shell entries for those two keys. If you do not restart the computer after you delete the Winsock keys, the next step does not work correctly.

Step 2: Install TCP/IP

1. Right-click the network connection, and then click Properties.
2. Click Install.
3. Click Protocol, and then click Add.
4. Click Have Disk.
5. Type C:\Windows\inf, and then click OK.
6. On the list of available protocols, click Internet Protocol (TCP/IP), and then click OK.
7. Restart the computer.

http://support.microsoft.com/kb/811259

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Another method to reinstall TCP/IP is this:

To Reinstall TCP/IP do the following:

Navigate to: C:\windows\inf
Find the File: nettcpip.inf
Right click the file and choose install

http://www.tweakxp.com/tweak1016.aspx

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And if the above still doesn’t work, then try this:

1) netsh int ip reset resetlog.txt

http://www.petri.co.il/reinstall_tcp_ip_on_windows_xp.htm

2) And the same reinstall of TCP/IP

a) Right click your network connection

b) Choose Properties

c) Click Install

d) Click Protocol and click Add

e) Click Have Disk

f) Type c:\windows\inf and click OK

g) Choose TCP/IP from the list of protocols

h) Click OK and restart the PC.