The error 651 message is common on Windows 7 through Windows 11 and usually appears in a small pop-up window. The actual text varies a bit, depending on the cause of the connection problem, but it always includes this text:

Although annoying, error 651 is a relatively minor problem and shouldn't cause a computer to shut down, restart, or display the blue screen of death.

Error 651 indicates that an attempt at a connection to the internet was unsuccessful, or an existing connection has been terminated. A variety of issues can trigger the alert, from incorrect placement of an SYS file, erroneous modem setup, corrupted registry files, an IP address conflict, and driver problems to issues with your internet provider.

Given the number of issues that can cause the Error 651 message, there are many approaches you can take to solve the problem. Here are a few things to try.

Test the connection on another device. It's the easiest way to check if the problem is related to your Windows computer, modem, or service provider.

If you can connect another device to the same Wi-Fi network, the problem lies with the computer. If you can't connect anything else to the same network, the modem, router, or provider is the problem.

Try a different connection. If you can't connect with another Wi-Fi network that you know is working, the problem is the computer. If you can, the connection is to blame.

Check for loose cables. Ensure all power and connection cables are plugged in securely to the computer, modem, router, and wall. This step might seem obvious, but connections come loose.

Reboot the modem and router. Unplug both devices, wait a minute, then plug in both devices. This might take a few minutes.

Restart the computer. This tech tip is a classic for a reason. It fixes a range of temporary glitches and errors.

Run the Internet Connections Troubleshooter. All versions of Windows have a built-in internet troubleshooting tool.

Ensure the modem, router, and associated cables are connected before running the Internet Connections Troubleshooter.

Check for Windows updates. Go to Settings > Update & Security > Check for updates. The Windows update process installs the latest features and security updates. It also scans the computer, fixes errors, and downloads any files that might be missing or corrupted.

Update the network adapter driver. Drivers help hardware run correctly. Installing a newer one, if available, could solve the internet connection problem.

Disable antivirus software. Some antivirus software can prevent Windows computers from connecting to the internet. Pausing the antivirus program or turning it off can fix internet connection issues.

Try these Windows commands. First, you'll need to open Command Prompt. In the Windows search bar, type Command prompt, then select Run as administrator. Next, type these command prompts, pressing Enter after each:

This command resets the Windows networking stack.

This command disables autotuning.

This command re-registers the raspppoe.sys file.

Restart the computer, and check the connection.

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