Well, Bhikkhu Pesala, if you have it then I should be able to get it!
You pointed me in the right direction and I went off to the Microsoft KB for an answer which was right there:
Using the > “A word or phrase in the file” > search criterion may not work Article ID : 309173 Last Review : May 2, 2005 Revision : 3.1
SYMPTOMS
When you search for files that contain text by using the > A word or phrase in the file > search criterion, the search results may not contain files that contain the text that you specified. For example, .log, .dll, .js, .asp, .xml, .xsl, .hta, .css, .wsh, .cpp, .c, or .h files, or files with no file name extension, may not appear in the search results even if the files contain the text that you specified. This problem may occur even if you specified the file name or type in the All or part of the file name box.
CAUSE
A filter component is not registered for the file type that contains the text that you specified, …
The list of file types did not include TTF or OTF. The fix was to update the Registry.
If no program that provides a filter is available, you can use the plain text filter for a file type.
To do this, add a PersistentHandler key under the file type key in HKEY_CLASSES_ROOT and set its (Default) string value name to the following value:
{5e941d80-bf96-11cd-b579-08002b30bfeb}
I found an entry for TTF files and changed the value and everything worked correctly. Now I have to enter one for otf files.
Better to read the article and not take my word for it.
And you’re right, it was a change made for XP.
Dick