November 11, 2026

Windows 10 Error 1500 Another Installation Is in Progress: Clearing a Stuck Background Install

You try to install a program and immediately see “Error 1500. Another installation is in progress. You must complete that installation before continuing this one.” But you are not installing anything else. When Windows 10 error 1500 another installation is in progress appears, Windows Installer believes a previous setup never finished.

Windows Installer can only run one MSI installation at a time. While a package is installing, updating, or rolling back, other installers must wait. Windows tracks this with a running process and a small “in progress” marker in the registry.

If an earlier install crashed, was cancelled, or is quietly running in the background, such as an Office update or a silent driver package, the marker stays and blocks new installs.

Ending the stuck process or clearing the marker lets new installations proceed.

The message often appears right after sign-in, when slot88 Office, Adobe, or a graphics driver is updating silently in the background, which is why it can seem to come and go.

Possible Causes

Error 1500 appears for these reasons:

• Another installer, such as an update, is genuinely running in the background.
• A previous installation crashed and left msiexec.exe running.
• The InProgress registry key was not removed after a failed install.
• Windows Update is installing components at the same time.

Waiting a few minutes after start-up is worth trying, because many programs update themselves silently right after you sign in.

Quick Fixes to Try First

Let other installs finish or end them.

1. Wait 10 to 15 minutes, then try again.
2. Open Task Manager and look for Windows Installer or msiexec.exe in the Details tab.
3. If no installer window is visible, right-click msiexec.exe and choose End task.
4. Restart the PC, which clears most stuck installations.
5. Check Windows Update and let any pending updates finish first.

If you are not sure whether an install is really running, open Task Manager’s Details tab and sort by name. Several msiexec.exe entries are normal during an active install, but a single entry using no CPU for a long time usually belongs to a stuck one.

Advanced Steps for Stubborn Cases

Clear the leftover marker.

1. Press Windows + R, type regedit, and press Enter.
2. Go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer.
3. If a subkey named InProgress exists, right-click it, choose Export to back it up, then delete it.
4. Also check HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager for a PendingFileRenameOperations value, which a restart should clear.
5. Restart and run the installer again.

If errors continue, set the Windows Installer service to Manual and restart it in services.msc.

Before You Go Further: Keep Your Files Safe

Do not end msiexec.exe while a visible installation window is still working, since that can leave software half-installed. Export registry keys before deleting them.

Conclusion

Error 1500 means Windows thinks another installation is running. Wait, end stray msiexec.exe processes, restart, and remove the InProgress registry key if it remains.