Question : Connecting to the Internet

Added new cable modem, new router, and three machines to the router.  First PC is hardwired to the router and it functioning perfectly, second machine (a laptop) is connected and functioning perfectly.  The third PC is the problem.  The wireless connection is successful on the third machine, and you can successfully ping the router; however, going beyond the router is the problem.  Additionally, in order to make the connection to the router, I had to manually input the ip information.  For some reason dhcp is not functioning correctly on the machine.  The pc is running XP SP2 and has been patched.  Additionally, firewalls have been turned off.  The cable modem, router and machine have been refreshed by powering off and on in order (too many times to count).  Any thoughts on what could be happening?

Answer : Connecting to the Internet

>  It won't even connect to the router when it doesn't have the IP info manually input.

Does it see the router's SSID in View Available Wireless Networks?

You did 'Remove' the router's profile from the Wireless Networks tab (right-click the wireless card in Network Connections and choose Properties), right?
Otherwise it doesn't help to disable security on the router, because the card will still be sending the security info saved in that profile, which won't match 'no security', of course.

If you followed the 'security checklist' in the manual when you set it up, you may have enabled the MAC filter too. Disable that as well. That's not much of a security measure, anyway, since MAC addresses are easily sniffed and spoofed.

After it tries to connect with 'Obtain an IP Address Automatically' (and you do the Repair, or release and renew manually with ipconfig), please open a command prompt window (Start->Run, type in CMD and hit Enter), and run the command
ipconfig /all >C:\ipconfig.log
then connect that computer to the router with a cable and upload that log file using the Attach File option below the message box here.