The windows installer service is unavailable

I got this error when I was trying to install any application, I didn’t know if this error is a bug in Windows Vista Ultimate or a bug in Windows Installer.

However finally I got the solution after days of searching Google to get any solution for this error but I didn’t find any.

What I have discovered so far is an application or registry entry I don’t know, it starts the Windows installer process not the service and keeps it running so when you try to install it gives you this error:

“Another application may be running setup. Finish any installation in progress, or restart your computer and re-run the setup”

It feels that you are running another setup!

In order to solve this issue and run your setup just end the Windows Installer Process from the Task Manager.