MSIDXSErrorLookup.1

Specified Program Identifier does not exist: MSIDXSErrorLookup.1
{F9AE8981-7E52-11d0-8964-00C04FD611D7}\ProgID

This ClassID key refers to Indexing Service, which makes part of Windows.
It's ProgID subkey refers to non-existent key. It has probably been left since the previous versions of Windows.
In any case, the link that refers to a non-existent key can be easily deleted.

AMUST Registry cleaner will delete obsolete ProgID subkey.
Note: When Indexing Service is enabled, it will restore the whole ClassID key, including invalid ProgID subkey every time the service is started.
So if you are using this service, you may want to add this issue to ignore list.