1618
App Installer (MSI)
Another Installation Is Already in Progress
Applies to: Windows 7, Windows 10, Windows 11
What it means
Windows Installer thinks another install is running, even if nothing visibly is — usually a stuck installer process from a previous attempt.
Also seen as: error 1618
Quick fix steps
- Restart the PC, which clears most stuck installer locks.
- Check Task Manager for any lingering "msiexec.exe" process and end it if the restart didn't clear it.
- Retry the installation after confirming no installer processes are running.
For the full step-by-step walkthrough, see An App Won't Open.
Frequently Asked Questions
Does this mean I have to close every open program?
Just the installer that's currently running or stuck — checking Task Manager for a lingering msiexec.exe process and ending it is usually enough, without needing to close unrelated programs.
Will this happen every time I install software?
No — it specifically means another installation was already in progress, which is an occasional conflict, not a persistent problem with your system.
Other error codes
1603 — Fatal Error During Installation
A generic installer failure code — the real cause is almost always in the detailed install log, but common triggers are permissions, a locked file, or insufficient disk space.
1618 — Another Installation Is Already in Progress
Windows Installer thinks another install is running, even if nothing visibly is — usually a stuck installer process from a previous attempt.
1601 — The Windows Installer Service Could Not Be Accessed
The Windows Installer service itself isn't running or responding.
1602 — User Cancelled Installation
The installer detected what it interpreted as a cancel action, sometimes triggered incorrectly by antivirus software or a UAC prompt timeout.