If you want to check the country database (or your log) for errors, you'll need to follow the following steps, described in more detail below:

Note that the procedure described below is only for analyzing country file differences. There is no need to export/import when installing a new country file.

Flam, OZ1AXG wrote a utility to identify logbook differences between two country files by exporting your log in ADIF format. You can download his program by following this link.

Detailed Instructions

  1. Export your log using your old (current) country file. This will create a log containing all your country mappings.
     
    In the main DX4WIN menu, go to File | Import/Export. After the filters come up, select the highest-number DX4WIN# format available. Now in the Import/Export Filters window, go to File | Export. Save the log under any name (I use my callsign). Note this log is a different format than the .DXL file (with a different extension), so it's OK to use the same name as your log, just do NOT give it a .DXL extension and over-write your log!
     
  2. Exit DX4WIN
     
  3. Copy your existing DX4WIN.CTY file from the SAVE directory to your ..\BACKUP directory. Newer installations of DX4WIN may not have this directory. If it doesn't already exist, create it yourself.
     
  4. Download and install the new country file by following the instructions here
     
  5. Start DX4WIN
     
  6. In your preferences, on the Import tab, ensure that "Accept DX4WIN values" is selected, and all three boxes are checked. If you make any changes, be sure to save them!
     
  7. Then File | New to create a new log. Pick a different (unused) name than before. You will probably not want to keep this log.
     
  8. Import your log using the new country file. This will identify any changes in your country mappings.
     
    In the main DX4WIN menu, go to File | Import/Export. After the filters come up, select the highest-number DX4WIN# format available (the same format you used to export the log in step #1 above). Now in the Import/Export Filters window, go to File | Import. Double-click on the name of the file you exported in step #1 above - it should have a .DXQ extension. Note the number of import errors that were detected.
     
  9. Now in this new log, use the F8 key to search the "Notes for this QSO" field for the word "import" (version 8) or "error" (version 7 or earlier). You will probably see some differences. In my own log, I had 3 differences out of 65K QSOs. Your mileage may vary. Check the differences against your QSL card collection. If you think they are real errors, please let me know. Many errors will be Zone errors, but the ones I'm most interested are the Pfx errors.
     
  10. Bring up the Logbook Editor (Window|Logbook). This will already be filtered to show only the error QSOs. Right-click on the logbook window and use the Report Editor to display only the following columns: 
    Callsign
Date
Country
Zone
Conf
QSO Notes
  11. Right-click on the report and select "Write to File". Give it a name (like your callsign).
     
  12. Using a spreadsheet program like Microsoft Excel (you can also use a plain text editor, but the fields are harder to see), examine the file for differences. The "Country" column reflects the entity in the new database, and "OtherPFX" errors in the "QSO Notes" column reflect the entity in the old database. In most cases, the new database will be correct. If you think it is not correct, verify the QSO with a QSL. If the QSL does not match the new database, please send me the details: callsign (as printed on the QSL), date, entity or island name (from the QSL card) and any other supporting information like CQ zone, IOTA, oblast, etc. Please don't send me the entire .CSV file, I do not have time to re-verify all the changes.

If you want to restore your old country file when you are done, exit DX4WIN, copy the DX4WIN.CTY file from your ..\BACKUP directory (see #3 above) back to your SAVE directory, restart DX4WIN and open your original log.