I am assuming you are using windows and not MAC? Since you have stated you are using MS access file format, it should be PD 6.2. There is no way to convert the file format that I am aware of.
You will need to "clean" uninstall PD 6.2 and install PD 4.1.4e.
After you install 4.1.4e, create the same username you had on the previous install of PD, close PD, navigate to c-program files-palm and find the username folder. Paste the address.dat file you have into the address folder in the username folder. Open PD and see if the data is there.
Create a new folder on your PC somewhere that is convenient. Name it something like Palm Desktop Data. (If you need help on the export the manual details are here)
Make sure you select all for the range in the export window.
With the data saved in the folder you created, make a copy of that folder and save to a flash drive, cd-rw or external hard drive.
Anytime you make a change in Palm Desktop, export the data that was changed to that folder and save again to the external media.
With this process you can always import the data back into Palm Desktop anytime you have a problem with the data in Palm Desktop or if your computer/hard drive/device crashes.
I hope that helps and I have answered everything.
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