A data diff tool for finding the difference between two Access MDB Files

See the following page and go down a bit for a list of utilities to compare Access databases http://www.granite.ab.ca/access/thirdparty.htm One of those might be what you're looking for.

I wanted to do the same (basically use DIFF to see differences row by row) so

1) I exported all the tables:

Option Explicit Option Compare Database

Private Sub ExportAllTables()
    Dim myDatabase As Database
    Dim myTableDef As TableDef

    Dim strTableName As String

    Set myDatabase = CurrentDb
    For Each myTableDef In myDatabase.TableDefs
        DoEvents
        strTableName = myTableDef.Name
        DoCmd.TransferText _
            acExportDelim, _
            , _
            strTableName, _
            Environ("USERPROFILE") & "\DeskTop\dump\" & strTableName & ".CSV", _
            True
    Next myTableDef
    MsgBox "Done"
End Sub

2) concatenated them into one file

type *.csv > all.txt

CAT will do as well if you have it

3) diff'ed them

diff all.txt all2.txt

I've made an AccdbMerge utility that is able to compare data and programming objects as well. In scope of "row by row" comparison - it will show what records were added/modified/removed, for modified records it will highlight fields with updated values.

Try using SQL Data Compare from Redgate, http://www.red-gate.com/products/SQL_Data_Compare/index.htm

and then use this trick, http://www.red-gate.com/messageboard/viewtopic.php?p=15296#15296