First of all,free download a contact backup program here:
The followings are step-by-step guides of how to backup contact:
Step 1. Click "start" and then select programs.
Step 2. Run "ContactsBackup".
Step 3. Click “Backup” button
Now you will want to input a backup file name, select folder, choose a backup file type(txt file or cbf file) and select a save location.
Step 4. Then click ‘Save’ to start backup
Step 5. After backup completes, you can see the backup file on your phone and transfer it to your computer easily by ActiveSync.