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 MaxCatalogs entry is the maximum number of catalogs that Indexing Service can open at one time.
|Range:||1 - 1000|
The value of an identically named entry under the Catalog subkey for a specific catalog cannot override the value of this entry.