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Please note that Microsoft has now released an official tool to resolve these issues, without the problems that previously existed with MSIZAP.
Take a look at a tool called MSIZap released by Microsoft.
UPDATE:
MsiZap.exe has been deprecated for quite some time. Its use is unsupported on all recent versions of Windows, and it is considered a very unsafe tool to use.
I added a link to a newer Microsoft support tool designed to clean out installations, but this tool also appears deprecated at this point. I have removed the link from the comments section.
Perhaps try the tool linked to in saschabeaumont's answer below.