Today I have troubleshooted a system (Windows XP SP2) with a Windows Installer error. The error reported both in Event logs (System log) is
The Windows Installer service terminated with the following error:
The requested lookup key was not found in any active activation context.
When manually (with services.msc) trying to start the service the following error comes up:
Could not start the Windows Installer service on <computername>.
Error 14007: The requested lookup key was not found in any active activation context.
The problem seems to relate to Windows Installer not correctly registered on the computer. Running the following commands solved the issue: