The Elvidge Family

"The Windows installer service could not be accessed." when installing/unistalling itunes

It took me ages to find the solution to my iTunes which would not uninstall/install - see here (or copied text below)

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"Everytime we tried to install itunes we would receive this error:

"The Windows installer service could not be accessed. This can occur if you are running windows in safe mode, or if windows installer is not correctly installed. Contact your support personnel for assistance"

Actually, everytime we tried to install any 64bit program we would receive this same error. I searched high and low and tried countless solutions.
Unregistering and reregistering the installer service, stopping and restarting, using theWindows Installer cleanup utility, etc...none of these things helped.

Today I came across a blog "Think#Knowledge Blog" that SOLVED my problem.

This is the solution that worked for me:

Go to this registry key:


HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSIServer

Look for

WOW64 and it's value.
Is it 0x00000001 (1) ?

This value tells Windows Installer only to deal with 32-bit installers and to return you an error whenever you try to install something that is 64-bit. To fix it, just set the value to 0. So you will see in your editor:

WOW64 REG_DWORD 0x00000000 (0)

After changing the value to zero, restart your Windows Installer Service by using services.msc or reboot.

This simple solution of changing the 1 to a 0 allowed me to finally install Itunes on Vista 64.

I hope this helps someone else who is having the same problem as this solution took me over a month to find."