This is actually very easy. Pseudo-code:
code:
For each section in INI1
 Read Section From INI2
 THEN
  For Each Entry in Section in INI1
   Read Entry in INI2
   THEN
    If entries do not match print "Dont match"
   ELSE
    Print "Entry missing in INI2"
 ELSE
   Print "Section missing in INI2"
Now repeat, swapping the ini files around, and don't bother to print the mismatched lines again as they will just be repeats from the first pass.