Indexing Service is no longer supported as of Windows XP and is unavailable for use as of Windows 8. Instead, use Windows Search for client side search and Microsoft Search Server Express for server side search.
The ISAPIDefaultErrorFile entry specifies the full virtual path to the generic error template.
If a value for this entry is not specified, a generic error page is used.
The value of an identically named entry under the Catalog subkey for a specific catalog cannot override the value of this entry.