A desktop on my workbench had a perfectly healthy Wi-Fi connection, but its Ethernet port acted like it had never met a network cable. That is the usual shape of wifi working but no ethernet: the internet service is fine, the router is alive, and the wired connection is the problem. Do not start by reinstalling Windows. Start with the physical path, then work toward drivers and settings.
Check the simple hardware first
Shut the PC down and inspect both ends of the Ethernet cable. Look for a loose connector, bent plastic tab, or cable that has been crushed behind a desk. Cat5e cable is plenty for ordinary gigabit networking, so you do not need a fancy braided Cat8 cable to solve this. Swap in a known-good cable instead. A short cable from another working computer is ideal.
Watch the lights beside the Ethernet jack on the motherboard. Most boards have green, amber, or blinking indicators when a link is detected. No lights usually means the PC and network device are not negotiating a connection. Move the cable to another LAN port on the router or switch. If the second port works, the first port is the suspect. If neither works, test that same cable with a laptop, game console, or another desktop.
The pattern matters. If the cable works elsewhere but your desktop reports wifi working but no ethernet, focus on the PC. If no device works from that router port, focus on the router, switch, or cable run. Do not replace a motherboard before doing this ten-minute test.
Confirm Windows can see the adapter
Press Windows key plus X, open Device Manager, and expand Network adapters. You should see a wired controller with a name such as Realtek PCIe GbE Family Controller, Intel Ethernet Connection, or a similar model. A yellow warning icon means Windows has detected trouble. A missing adapter can mean a disabled device, missing driver, BIOS setting, or failed hardware.
Right-click the adapter and choose Enable device if that option appears. If it is already enabled, select Properties and read the Device status box. Error codes are useful clues, but do not treat every code as proof that the motherboard is dead. Windows driver corruption is common after a major update, a fresh installation, or a motherboard replacement.
Download the wired LAN driver from your motherboard maker's support page using another device if necessary. Copy it with a USB drive, install it, and restart. For an ASUS, MSI, Gigabyte, or ASRock board, use the exact board model, not just the chipset family. The wrong package can install poorly or leave the adapter unusable.
Reset the adapter without burning down the network
Open Settings, select Network and Internet, then Advanced network settings. Make sure Ethernet is not disabled. You can also open Control Panel's Network Connections panel and verify that the wired adapter is enabled. A gray adapter icon is an easy fix; right-click it and choose Enable.
Next, open Command Prompt as administrator and run these commands one at a time:
ipconfig /release
ipconfig /renew
ipconfig /flushdns
The first two request a new address from the router. The third clears stored name-lookup information. These commands help when the Ethernet adapter connects but cannot reach websites. They will not repair a snapped cable or a dead jack, so keep the physical checks in the picture.
If wifi working but no ethernet continues after that, use Windows Network Reset as a last software step. It removes and reinstalls network adapters, so you will need to reconnect to Wi-Fi and possibly reinstall a VPN. Save that job for after driver and cable testing, not as the opening move.
Check speed, duplex, and power settings
In Device Manager, open the Ethernet adapter's Properties and inspect the Advanced tab. The Speed and Duplex setting should normally be Auto Negotiation. Forcing 100 Mbps or Full Duplex can create a mismatch with a gigabit router or switch. Change an unusual manual value back to Auto Negotiation, click OK, and restart the connection.
The Power Management tab can also contain a useful test. Temporarily clear “Allow the computer to turn off this device to save power.” This is not always the permanent answer, but it can expose a sleep-resume problem on older drivers or budget network controllers. On a desktop that stays plugged in, saving a tiny amount of power is not worth losing the wired connection.
Look at the adapter's status window. A 169.254.x.x address means Windows did not receive a normal address from the router. That points toward DHCP, the cable, the router port, or the adapter. An address such as 192.168.1.x or 10.0.0.x means the PC joined the local network, so the remaining problem may involve DNS, firewall rules, or the router's internet connection.
Separate a PC failure from a router failure
Test the computer with a different network device. A basic unmanaged gigabit switch costs roughly $15 to $30 and is useful for this exact diagnosis, but you do not need to buy one immediately. Borrow one, connect the router to the switch, and connect the PC to another switch port. If the link appears, the original router port or its configuration is questionable.
Test the PC on a different router or a friend's network only if that is practical. Another clean test is a USB-to-Ethernet adapter from a reliable brand such as Anker, Plugable, or TP-Link. If the USB adapter works immediately, the built-in Ethernet controller or its driver is the likely culprit. If the USB adapter also fails, look harder at Windows, the cable, or network equipment.
For a new custom build, enter the UEFI or BIOS and confirm onboard LAN is enabled. The label may be Onboard NIC, Integrated LAN, or Network Controller. Builders sometimes disable unused devices while changing boot settings, then forget what they changed.
When replacement is the sensible fix
A failed Ethernet controller is not automatically a motherboard replacement. A PCIe gigabit network card often costs about $20 to $40 and takes minutes to install in a spare slot. A USB adapter is even simpler and works well for office computers, though a PCIe card is the cleaner long-term choice for a gaming or workstation build.
Before buying anything, confirm that the router, cable, and driver tests point toward hardware. A new adapter will not fix a bad switch port. Likewise, replacing a router because wifi working but no ethernet appears on one desktop is backwards troubleshooting.
I have fixed this exact complaint with a $7 cable, a disabled Windows adapter, and one forgotten BIOS setting. The cure was different each time because the symptom was the same, not the failure. Run the tests in order: cable, port lights, Device Manager, driver, adapter settings, then alternate hardware. That keeps a small network problem from becoming an expensive parts pile.
If wifi working but no ethernet is still the result after those checks, connect a USB Ethernet adapter and get the machine stable first. Then replace the built-in controller only if the evidence earns it. I turn it on so you don't have to.
