Can't open thesaurus in Word 2003

[PROF]

When trying to use thesaurus error message states that Word can't install
thesaurus due to Windows Installer error 1605. This action is only valid for
products that are currently installed.

I have done all I can find on the Internet to do, including uninstalling and
re-installing Office 2003 three times...using different variations, i.e.,
repair, complete install, customized install making sure all Word options are
checked, etc.

It seems like it's a Windows intall error. Can anyone help me? Thanks!