I could get all fancy about it but you have good advice already. Invariably when you get an unexpected "Enter Parameter xxxx" pop-up and you think it is something you removed, you missed a spot in your cleanup. It's a leftover reference to whatever is named.
Where to look:
Tables? Not likely because tables don't directly reference other tables very often. You would likely know if you had done this.
Queries? Possibly so, in any place including primary field selection, JOIN clauses, WHERE clauses, ORDER BY and GROUP BY clauses, and HAVING clauses - all of which allow individual field names as members of their clause types. If you get all of the queries printed out in SQL view it should be relatively easy to find it if it is there. See also the "Database Tools" "Documenter" option which can do the SQL "dump" for you.
Relationships? Rare, but I suppose it is possible. The "Database Tools" "Documenter" can list your relationships for you, which might help.
Forms? Look in any field bound to a record AND any field that has a formula. But ALSO look for any control that has a ControlSource that does not correspond to fields in the RecordSource.
Reports? Same as for Forms but also look at report SORT and GROUP options, which can be confusing because of how they are implemented.
Macros? Could happen. No choice but detailed examination one macro at a time.
Modules? Could happen - but fortunately for modules, you can do a whole-project search for the thing that was named as the missing parameter and either find it right away or eliminate all modules as possible culprits in a single search.
