All morning long I’ve been battling my Windows 7 system. I finally found out that the error code which reads:

“Error 1500. Another installation is in progress. You must complete that installation before continuing this one.”

can be attributed to the InProgress key found in the registry at


After doing a little searching on the web, I found that Microsoft has a program called msizap.exe which can be found in the Windows Installer SDK. The problem with that is that the SDK itself is an .msi file. I didn’t really want to install the full SDK anyway. So I searched some more and came across the Windows Installer Cleanup Utility. This was mainly created to clean-up an Office installation gone bad. Again, an .msi file. So, I went back to the Windows Installer SDK and downloaded it. To trick the system into letting me install it, I simply deleted the key mentioned above (HKEY\_LOCAL\_MACHINE\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Installer\\InProgress). At first attempt, I received an error. I tried deleting it again and it worked. Went through the installation process only to receive the same error. After I refreshed the registry, I saw that it was back. It pointed to a .ipi file contained in the C:\Windows\Installer directory. At this point, I still don’t know what this installer is that is still hung up. I opened several of these files from today and the reference Visual Studio 9.0. I’ll see if I can track down what is later.

Anyway, I finally decided to quick hit delete on the key and then quickly hit retry on the installation. It worked. My installation continued. At the very end a refresh of the registry showed that the other application came back and added an InProgress key again.

Back to the msizap.exe application. On the surface, if you use the p switch like

msizap p

It appears to only delete the key in the registry just like the above. I saw that in my case, the InProgress key still comes back. I guess it’s purpose is so that you don’t touch the registry.

I’ll add an update to this post if I find out how to completely kill that other installation package.