KB5120998 black background? Install the Windows 11 fix

Match the exact issue

This guide fits a narrow symptom. The Windows desktop loads, the taskbar and icons remain usable, and the background has changed to a solid black color. The problem began after an update released August 27, 2026, identified as KB5120998 or OS build 26100.9278 or 26200.9278.

Microsoft reports that the update can prevent some desktop settings from loading. Slideshow settings or contrast themes may also be affected. Repeatedly choosing the wallpaper does not solve the pre-fix state because Windows is failing to load the setting, not simply forgetting which picture you picked.

Write down what still works, the first date you saw the black background, and whether other personalization settings changed. Timing supports the match, but it does not prove the update is responsible unless the version, build, and symptom line up.

Check your version and build

Press Windows + R, enter winver, and select OK. Record the Windows version and OS build shown in the About Windows box. This incident applies to Windows 11 version 24H2 and version 25H2. Microsoft lists no affected Windows Server platform.

• 24H2 on build 26100.9278, or a later build before 26100.9445. The confirmed issue can match. Check Windows Update for KB5124008 or a later security update.
• 25H2 on build 26200.9278, or a later build before 26200.9445. The same resolving update applies.
• 24H2 build 26100.9445 or later, or 25H2 build 26200.9445 or later. The fix should already be present. Move to the verification section.
• Another Windows version, no usable desktop, or no matching update timing. Do not force this incident to fit. Use the route for the actual symptom.

You can also open Settings, choose Windows Update, then Update history to record the installed KB numbers. If Settings will not open, use the Windows Settings guide rather than deleting settings or resetting the PC.

Install the resolving update

Open Settings, choose Windows Update, and select Check for updates. Install KB5124008 if it is offered, or install the current later security update for your supported Windows version. Microsoft distributes KB5124008 automatically through Windows Update and Microsoft Update.

Leave the computer connected to power and let Windows finish. Do not interrupt the update because the background remains black during installation. If Windows Update reports an error, preserve the exact code, update name, download percentage, and stage. Then use the Windows Update guide for that separate problem.

Managed devices may receive updates on an administrator's schedule. Do not bypass Windows Update for Business, device-management policy, or an organization's approval process. Give the administrator the current build, KB5120998 timing, and the Microsoft release-health link from the sources below.

Restart and verify

Restart when Windows asks. After sign-in, wait for the normal desktop to finish loading. Run winver again and confirm build 26100.9445 or later on 24H2, or 26200.9445 or later on 25H2.

Check whether the expected wallpaper, slideshow, and contrast theme now load. If the desktop is usable but still shows the black background, select the intended background once through Settings, Personalization, then Background. Restart once more and check the same account.

Record the build after the update and whether the background returned before or after you selected it again. This readback distinguishes an update that never installed from a fixed system that still needs its preferred background selected.

Route a different black screen

A solid black wallpaper is not the same as a black display or an incomplete sign-in session. If there is no taskbar, no desktop icons, no cursor, no signal, a flashing display, or a screen that goes dark before sign-in, stop using this guide.

The Windows black-screen-after-login guide uses the cursor, security screen, display mode, Explorer, driver, profile, and startup clues. Preserve any working display and unsaved work before changing projection modes, graphics drivers, profiles, or startup settings.

Do not assume KB5120998 caused a different black-screen state because the dates overlap. The confirmed Microsoft incident is about desktop personalization settings on an otherwise usable desktop.

If the background stays black

First confirm that the resolving build is really installed. Then test one local account and one simple built-in picture or solid color through the normal Personalization page. Record whether every background type fails, one account is affected, or only a slideshow or synced theme fails.

Check for organization policy or accessibility settings before changing system files. A managed wallpaper, contrast theme, damaged image path, account-specific setting, or a different shell problem needs its own evidence. Do not use a registry cleaner, policy bypass, third-party driver updater, or full Windows reset as a shortcut.

If the fix is installed and the same narrow issue persists, use the Get Help or Feedback Hub app and include the Windows version, OS build, installed KBs, account scope, personalization type, and exact result after restart. Remove user names, email addresses, organization details, and private file paths from screenshots or logs.

Where OmniMend fits

On a supported Windows 10 or Windows 11 x64 PC, OmniMend can organize non-secret operating-system, update, hardware, and timeline evidence around the symptom. It does not install KB5124008, repair Windows personalization, change a wallpaper, override organization policy, or prove that KB5120998 caused a different black screen.

Windows Update and Microsoft's release-health guidance are the fix path for this incident. If you want a separate record of the local PC after the update, download OmniMend, then review and redact the report before sharing it. Keep account names, private paths, organization data, and other sensitive details out of the record.