After the fact, you need to modify the one in <index file
location\SSP\GUID\12\config>(sp?). I don't have an image around, so
that could be off a little. You need to modify it on every query server
in the farm, and for each Shared Services Provider in the Index file
location. If you were to do this before scaling to query servers, they
would be copied at query server creation time.

Thanks. I edited all 4 copies of the thesaurus  file found by search
on the whole file system on the search server (only one search server
in the farm, in fact the farm consists of a database server and the
other server is running everything else). Two of the files were in
the same directories that contained index files, so I think I have
covered your suggestion.

I stopped all search services, and restarted them (Office Search,
Windows SharePoint Services Search, Windows Search). I did a Reset
All Crawled Content. I did a full crawl. There were no errors in the
crawl log, and the warnings made sense. The search works as expected,
but there is no effect of either the expansion sets nor of the
replacement sets.

Does anyone have any ideas how I can get this to work?

Is it possible that some file other than tsenu.xml is being used? I
did a standard installation, adding no languages, so I would think
that tsenu.xml is the right file, but what is tseng.xml for?

Tsneu.xml, perhaps. That is the default (neutral, I believe)

Thanks, but that doesn't help either.

I now have the same expansions and replacements in all occurences of
the following files: tseng.xml (International English), tsenu.xml (US
English), tsneu.xml (neutral language).

After reading KB 837847 I even added the
<case caseflag="false"></case>
in all the files because I realized I was testing by entering
lowercase query terms but had entered them into the thesaurus  as
uppercase terms.

I believe I have done everything that you and Microsoft and Bill
English document in trying to get this to work, with no luck.

Is anyone else successful with entering items in a thesaurus? Can you
show me an example of your thesaurus, and how you are testing that it
is working? I realized after reading KB 837847 that testing expansion
required an understanding of the difference between phrase search
and "FREETEXT" search. So testing is not a simple step.

Here is a sample of my thesaurus:

<XML ID="Microsoft Search Thesaurus">
<thesaurus xmlns="x-schema:tsSchema.xml">
<case caseflag="false"></case>
<expansion>
_{Help Desk}
_{Customer Service}
</expansion>
<expansion>
_PSO
_{Public Sector Organization}
</expansion>
<expansion>
_STP
_{Strategic Technology Plan}
</expansion>
<expansion>
_EAM
_{Enterprise Asset Management}
</expansion>
<expansion>
_CMMS
_WMS
_CWMS
</expansion>
<expansion>
_ESRI
_GIS
</expansion>
<expansion>
_{Operations Optimization}
_EWQMS
</expansion>
<expansion>
_{Sustainable Organization}
_{triple bottom line}
</expansion>
<expansion>
_IT
_{Information Technology}
</expansion>
<expansion>
_IS
_{Information Systems}
</expansion>
<expansion>
_CRM
_3-1-1
₃₁₁
</expansion>
<expansion>
_SCADA
_{Supervisory Control and Data Acquisition}
</expansion>
<replacement>
<pat>utilty</pat>
_utility
</replacement>
<replacement>
<pat>maintance</pat>
_maintenance
</replacement>
<replacement>
<pat>manger</pat>
_manager
</replacement>
<replacement>
<pat>pubic</pat>
_public
</replacement>
<replacement>
<pat></pat>

</replacement>
</thesaurus>

</XML>

Here is an example of my test query term: PSO

It returns only instances of PSO in documents, not including
instances of Public Sector Organization in documents.