Migrate content of cck fields from drupal 5 to 7
Once I had a same problem and after couple of hours testing/working with couple of approaches I figured out that the best way to deal with this is using views bonus pack module to get a CSV export file:


  This group of modules is sort of a recipe module that makes things
  easier by showing how to integrate some other modules as well as
  providing miscellaneous features that aren't distributed by Views
  itself. Sometimes these modules are only base recipes that will need
  to be themed and spiced up to fit your needs so be creative!


and import it via feeds module:


  Import or aggregate data as nodes, users, taxonomy terms or simple
  database records.