When modifying Thesaurus files there are a few things to note that may cause you problems.
· To get started read the following article: http://msdn.microsoft.com/en-us/library/ms345186.aspx
· The file that you should modify is at: [Drive]:\Program Files\Microsoft Office Servers\12.0\Data\Office Server\Applications\
· If the XML is malformed, SharePoint will throw an error which will be logged in the application event log. You will need restart the Office SharePoint Server Search service and try a query to get the error logs. Items that can cause this to happen are:
o Special Character will cause an invalid format error. More details on this can be found at: http://support.microsoft.com/kb/923317
o The thesaurus expansions and replacements no longer work if you have stemming turned on in the search results web part.
o Duplicate expansions with the same words