Note: This may work with other Nokia phones too depending on the version of Symbian OS that they use.  This method is so easy it’s quite unbelievable.

Here’s what you do:

  1. On your Nokia go to Contacts
  2. Go on Options > Mark/Unmark > Mark All
  3. Go on Options > Copy > To Memory Card
  4. Connect your phone to PC
  5. Browse to /Other/Contacts/ on your phone’s memory card
  6. Copy all the .vcf files to your PC
  7. Connect your Desire to PC and mount as USB
  8. Copy all the .vcfs to the SDCard (make a directory for neatness if you like)
  9. Open the People app on the Desire
  10. Press the Menu button and select Import/Export
  11. Select the Import from SDCard option
  12. Select the Import All vCard files option
  13. Ta-da!

All your contacts will now be on your Desire using really simple steps.
NOTE: This has been tested on an N95 and should work on other phones too.  It even worked on a Sony Ericsson K750i!

Credits to Teh Lemur for the original post

UPDATE 1: 15 April 2010 – 15:22: Updated the instructions on what to do on your Nokia