When you try to install/uninstall some application/s, you may get warning messages like:

"The Windows Installer Service could not be accessed"

"Windows Installer Service couldn't be started"

"Could not start the Windows Installer service on Local Computer. Error 5: Access is denied." Here are two methods to fix the problem.

Method 1
Unregister Windows Installer, and then reregister Windows Installer. To do this, follow these steps:

1. On the "Start" menu, click "Run:.

2. In the "Open" box, type "msiexec /unreg", and then press ENTER.

3. On the "Start" menu, click "Run".

4. In the "Open" box, type "msiexec /regserver", and then press ENTER.


Method 2
Upgrade to Windows Installer version 2 or newer version. To do this, follow these steps:

1. Start Microsoft Internet Explorer, and then browse to the following Microsoft Web site: 
   http://msdn.microsoft.com/downloads

2. In the left pane tree menu, click "Setup and System Administration", and then click "Setup".

3. Click "Windows Installer", and then click the appropriate link for your operating system.

4. Click "Download" to download and install Windows Installer version 2 or newer version.