Hmm... reread the whole thread.
I will need you to do something.
Can you please do an ipconfig on the PC that can't access
Internet?
Please enter ipconfig /all and post back the details.
This is an important step.
Edit: I'll just post everything.
After doing an ipconfig /all, note down the IP address.
If you get an IP address such as this: 169.254.y.z (y and z are
numbers from 0 to 255), a subnet mask of 255.255.0.0 and is using
Windows XP Professional, your IP address was assigned by the
Automatic Private IP Addressing (APIPA) feature of Windows XP
Professional.
This means that no DHCP server is found, and therefore, there would
be no default gateway.
If your IP address is returned as 0.0.0.0, the DHCP Media Sensing
feature override is turned on because the network adapter detected
its lack of connection to a network, or TCP/IP detected an IP
address that duplicates a manually configured IP address.
Now, if there's nothing wrong, proceed on.
Go to Start > Run and type in cmd
Type in this command: ping 127.0.0.1
If you get no replies, it means:
Try disabling your protection programs (antivirus, firewall,
anti-spyware) to make sure that nothing is interfering it. If it
doesn't work, it means a hardware problem or TCP drivers are
corrupted. Uninstall the TCP drivers and reinstall them. (XP CD is
needed)
Next, ping your router's address (192.168.1.1)
If this fails, it means there's a problem with your hardware
(definitely not router, your laptop works fine)
But don't troubleshoot hardware first. Proceed on to the next
step.
Open cmd again. Type in pathping yahoo.com. If
this fails, move on.
Open cmd and type in netsh interface ip delete
arpcache
Then redo all settings for this computer.
If you still get no default gateway, try a hard reset.
Some versions (like the BEFSR41) have a reset pin that you poke
with a paperclip end through a small hole in the front panel
labeled Reset. Some versions (like the BEFW11S4) have a reset
button on the back. You have to hold these down for about thirty
seconds to hard-reset the nonvolatile RAM. This will lose your
configuration settings.
http://www.faqs.org/docs/Linux-HOWTO/Linksys-Blue-Box-Router-HOWTO.html
http://www.tech-faq.com/forgot-linksys-router-password.shtml
