Are you exporting from and importing into Outlook Express?
If so it is easiest to use a WAB (Web Address Book)
To use, open O.E. and open "Addresses" to get Address Book and in their click on "File" and from drop down menu select Export > Adress Book (WAB) and save it to location you wish.
Save Desk Top on 2nd system and from within O.E.
navigate as before but choose Import > Address Book
(WAB) and import from desktop.
With CSV files you would still need to convert back into a WEB file anyway.