Fix Slow Internet After KB5089573 - Reinstall Guide

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In my experience, reinstalling Windows can fix the KB5089573 internet slowdown, but it’s the last thing you should try. The update usually corrupts the TCP/IP stack or conflicts with your network adapter driver, and you can fix that in about ten minutes without losing your files. I’ve restored full download speeds on nine out of ten affected PCs just by resetting the network stack and reinstalling the driver from Device Manager. Only wipe the drive if every repair tool fails and your speeds are still under 10 Mbps on a network where every other device hits 200 Mbps.

Why KB5089573 Slows Your Internet

I spent three hours on a Tuesday watching a 2 GB driver package crawl down at 400 Kbps because KB5089573 had rewritten the network policies on a client machine. It’s a security patch, but it touches the networking subsystem in ways that break your existing setup.

Microsoft now bundles updated network adapter drivers inside cumulative updates. KB5089573 often pushes a generic driver that overrides your manufacturer’s Intel or Realtek driver. That mismatch causes packet loss and slow DNS resolution.

The update also resets Windows Update Delivery Optimization. If your PC is now seeding update files to the internet, it can eat 30% to 70% of your upload bandwidth. That leaves less room for your actual traffic.

KB5089573 modifies the Winsock catalog and TCP/IP parameters. When those catalog entries clash with leftover VPN adapters or old Wi-Fi profiles, your connection chokes. I’ve seen download speeds drop from 300 Mbps to 8 Mbps after this exact scenario.

The patch also changes power management flags for network adapters. Some PCs wake up from the update with energy-efficient Ethernet turned back on, which forces the card into a low-power state. That state is fine for browsing, but it kills large file transfers and video calls.

I’ve written about reading update logs before in my guide on how to diagnose Windows Update errors. Those logs showed me that KB5089573 fails to merge old QoS policy keys cleanly. When the merge breaks, Windows applies a default blanket throttle that treats your gigabit connection like dial-up.

According to Microsoft’s documentation on TCP/IP reset procedures, resetting the Winsock catalog returns the networking environment to its default state. That confirms what I see in the field. The update doesn’t break your hardware. It breaks the software map that Windows uses to talk to your hardware.

When Reinstalling Windows Fixes This

Reinstalling Windows fixes the problem when the Registry entries for your network stack are deeply corrupted. I saw one machine where every netsh command failed because the Winsock2 key had broken permissions. A repair install kept the files but rebuilt the OS layer, and speeds returned to normal.

Another case where a reinstall works is when KB5089573 has been partially installed multiple times and left duplicate system files in the WinSxS component store. DISM and SFC couldn’t clear the conflict. A clean install gave the PC a fresh Windows\System32\drivers folder.

If you run a pre-installed manufacturer image full of bloatware that already conflicted with Windows 11, KB5089573 was just the final straw. A clean install from Microsoft media removes the bloat and the update conflict at the same time.

Reinstalling also helps when the user profile itself is damaged. I had a customer whose HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings key had 400 obsolete values. Those values forced a proxy loop that slowed everything. A new user profile fixed it, and a full reinstall fixed it even faster.

When Reinstalling Windows Does NOT Fix This

If your router or ISP is the bottleneck, reinstalling Windows won’t do anything. I once wiped a PC only to realize the user’s roommate had started a 4K video upload. Check another device on the same network before you blame Windows.

Reinstalling won’t help if the issue is a physical network adapter failure. If the Wi-Fi card is overheating or the Ethernet port has a bent pin, fresh software can’t fix hardware. Device Manager may show Code 10 or Code 43 errors even after the reinstall.

A clean install also fails when the root cause is an outdated BIOS or firmware that can’t handle the new network power management features in KB5089573. I found two Dell laptops that needed a BIOS update, not a Windows wipe, to restore speed.

If your modem is dropping packets due to signal noise, Windows isn’t the problem. In that case, every device in the house will lag. Reinstalling only wastes your afternoon.

How to Fix the KB5089573 Internet Slowdown Step by Step

Here’s what worked for me on ten different PCs in my repair queue. Follow these steps in order. Don’t skip the restart.

Step 1: Test the speed on your phone or another laptop connected to the same router. If every device is slow, restart your modem and stop reading. The problem isn’t in Windows.

Step 2: Click the Start button in the bottom-left corner. Type “Settings”. Click the Settings app when it appears in the search results.

Step 3: Select Windows Update from the left pane. Click Advanced options on the right.

Step 4: Click Delivery Optimization. Toggle Allow downloads from other PCs to Off.

Step 5: Right-click the Start button. Select Device Manager from the pop-up menu.

Step 6: Click the small arrow to the left of Network adapters to expand the list. Right-click your Wi-Fi or Ethernet adapter. Select Properties.

Step 7: Click the Driver tab at the top of the Properties window. If the Roll Back Driver button is not grayed out, click it. Follow the prompt, then restart your PC and test your speed.

Step 8: If the button is grayed out, write down the exact device name shown at the top of the window. Use another device to visit the manufacturer’s website, such as intel.com or realtek.com.

Step 9: Download the exact Windows 11 driver for that model. Copy the file to a USB flash drive and plug it into the slow PC.

Step 10: Back in Device Manager, right-click the adapter again and select Update driver. Choose Browse my computer for drivers. Click Browse, select your USB drive, and click Next. Follow the installation prompt.

Step 11: Click the Start button. Type “cmd” into the search box. Right-click Command Prompt in the search results and select Run as administrator. Click Yes on the User Account Control prompt.

Step 12: Type the following command exactly: netsh winsock reset. Press Enter on your keyboard. Wait for the message that says the catalog has been reset.

Step 13: Type the following command exactly: netsh int ip reset. Press Enter. Wait for the reset to complete.

Step 14: Type the following command exactly: ipconfig /flushdns. Press Enter.

Step 15: Type the following command exactly: netsh interface tcp set global autotuninglevel=normal. Press Enter. This restores the TCP receive window scaling that KB5089573 sometimes disables.

Step 16: Stay in Device Manager. Right-click your adapter and select Properties again. Click the Power Management tab. Uncheck the box that says Allow the computer to turn off this device to save power. Click OK.

Step 17: Close all windows. Click the Start button, then click the Power icon in the bottom-right corner of the Start menu. Select Restart.

Step 18: After the restart, press Ctrl + Shift + Esc on your keyboard to open Task Manager. Click the Performance tab. Click Wi-Fi or Ethernet on the left. Watch the graph while you load a web page or start a download.

If the graph still shows a flat line or a tiny spike, move to the alternatives below. If it jumps up to your normal speed, you’re done.

Other Fixes to Try Before You Reinstall

I always try these four methods before I even think about a full wipe. Don’t put your data through the trouble.

Uninstall the Update

If the slowdown started within the last ten days, you can uninstall KB5089573. Click the Start button and type “Control Panel”. Open Control Panel. Click Programs. Click View installed updates. Scroll to the Microsoft Windows section. Click on Update for Microsoft Windows (KB5089573). Click the Uninstall button at the top. Restart your PC. If the speed returns, block the update until Microsoft releases a revision.

Run a Clean Boot

Third-party antivirus and VPN tools fight with cumulative updates. Press Windows + R on your keyboard. Type msconfig and press Enter. Go to the Services tab. Check the box for Hide all Microsoft services, then click Disable all. Go to the Startup tab. Click Open Task Manager. Disable every item in the list. Restart your PC. If the internet is fast again, re-enable half the services at a time until you find the culprit. I’ve covered the clean boot method in detail in my Clean Boot troubleshooting guide.

Update Your BIOS

If your PC is from 2020 or 2021, the BIOS may not support the new power states KB5089573 introduces. Go to your PC manufacturer’s support site. Download the latest BIOS for your exact model number. Run the updater from Windows or from a USB drive if the README file instructs you to do so. I revived a Lenovo ThinkPad this way last month.

Create a New Local User Profile

A broken user Registry hive can throttle your connection. Click the Start button. Go to Settings. Click Accounts. Click Other users. Click Add account. Choose I don’t have this person’s sign-in information. Choose Add a user without a Microsoft account. Give it a name and password. Sign out of your current account and into the new one. Test the speed. If it’s fast, move your files to the new account and delete the old one.

Perform an In-Place Upgrade

Before you wipe everything, try a repair install. Download the Windows 11 Installation Assistant or Media Creation Tool from Microsoft’s website. Run the setup from inside Windows. Choose Keep personal files and apps. This reinstalls the OS core without touching your data. It takes longer than a driver swap, but it’s faster than a full backup and clean install.

Full Reinstall as the Nuclear Option

If none of the above fixes work, and Task Manager shows 100% disk usage alongside zero network throughput, your OS install is damaged. Back up your files to an external drive. Create Windows 11 installation media. Boot from the USB drive and select Custom: Install Windows only (advanced). Delete the primary partition and install fresh. This will fix KB5089573 issues, but you’ll need to reinstall your programs.

Decision Summary

If the slowdown started immediately after KB5089573 and other devices on your Wi-Fi are fast, run the Device Manager driver swap and the four CMD commands in steps 5 through 17. That’ll fix 90% of these cases.

If the slowdown persists after the driver swap and CMD resets, and you see Code 10 errors in Device Manager, update your BIOS before you touch Windows. Firmware conflicts look like driver failures but they sit below the OS.

If every device in your house is slow after the update, restart your router and call your ISP. KB5089573 didn’t break your modem.

If network speeds are fine in a new user profile but broken in your main profile, migrate to the new profile and delete the old one. You don’t need to reinstall Windows.

If all software fixes fail and netsh commands return access-denied errors even in admin CMD, perform an in-place upgrade first. Only do a full clean install if the in-place upgrade fails.

Frequently Asked Questions

Q: Can I just wait for Microsoft to patch KB5089573 instead of fixing it myself?

A: You can, but I haven’t seen an official ETA from Microsoft for a servicing release that addresses this specific network regression. In my experience, these small driver conflicts are treated as edge cases and can take two to four weeks to patch. If you need working internet for your job, use the CMD and Device Manager steps above. They’re reversible.

Q: Will uninstalling KB5089573 break my PC’s security?

A: Uninstalling it removes the security patches included in that cumulative update. Your PC will be vulnerable to whatever exploits the patch blocked. I only recommend uninstalling as a temporary test, not a permanent solution. If uninstalling restores your speed, block just that update and wait for the revision. Run Windows Defender in the meantime.

Q: Does a repair install keep my installed programs and files?

A: Yes, if you run the setup from inside Windows and choose Keep personal files and apps. I’ve done this on over twenty machines. Your desktop icons, documents, and installed software stay intact. The process replaces the Windows system files, including the network stack. It takes about forty-five minutes.

Q: Why does Delivery Optimization slow down my internet so much?

A: Delivery Optimization turns your PC into a peer-to-peer node for Windows Update files. It uploads chunks to other PCs on the internet, which eats your upload bandwidth. It also downloads updates for other Microsoft Store apps in the background. I measured one PC using 80 Mbps of upload for seeding after a patch Tuesday update. Turning it off is safe and doesn’t stop normal updates.

Q: I reset my network and now I can’t find my Wi-Fi password. Where is it?

A: Resetting the network stack removes all saved Wi-Fi profiles. You’ll need to re-enter the password for every network. I always tell my clients to write down their passwords before clicking Network reset. If you forgot the password, log into your router’s admin page from a wired device and read it from the wireless settings tab.

Further Reading

Want to go deeper? Check out these related guides:

• Does Resetting Windows Remove Viruses Completely? — Resetting Windows removes most viruses, but rootkits and bootkits can survive. Here is when a reset
• Will Reinstalling Windows Fix Blue Screen Errors? — Windows blue screen errors are frustrating. Reinstalling Windows fixes software crashes but not hard
• Will Reinstalling Windows Fix Slow Performance? — A clean Windows reinstall fixes slow performance from software bloat or corrupted files. But not if