I bought a Dlink wireless router, a wireless network card and 2 wired ethernet cards.
The 2 ethernet computers are using WinXP SP2 and the wireless computer is on Windows 2000.
The wireless and the ethernet desktop are working properly.
But the 3rd ethernet WinXP SP2 computer is not connecting properly and it can't surf the web or connect to the other computers files.
Can anyone help?
You're gonna have to goto Control Panel -> Network Connections on your 3rd computer. Right-click -> Properties on the LAN connection, and select TCP/IP and goto Properties. If "Automatically obtain an IP Address" isn't selected, that may be the problem.
There are other problems that can cause this, such as faulty cabling, using the wrong cable (you need a straight-through, not a crossover. You can check by comparing the pins), or a faulty port on the router.