the subquery I told you to write takes too long. I waited a minute for the thing to run on my laptop and stopped it because I got sick of waiting. For ''IN'' subqueries, you have to wait for the engine to perform <tableCount1> * <tableCount2> tasks before you get the result. So you would be asking for 68934 * 115641 = 7971596694 tasks to complete. Yeah, that's too long. 
So the alternative, which is always better than a subquery anyway, is to write an unequal Join. In your case, this will be fine:
Code:
SELECT DISTINCT [Inhouse Imagery].Pathrow
FROM [Inhouse Imagery] LEFT JOIN
[EDC Archive] ON [EDC Archive].Pathrow = [Inhouse Imagery].Pathrow
As a last note, use the compact and repair feature in Access. It's not practical to send someone a 500MB file when it's real size is only 10% of that. Gmail's servers probably weren't too happy with you either. 
That should be enough for you to mark this thread as solved, my dear.