Transfer old contact list to any format available that is recognized by MS Excel. tab delimited csv is probably the best bet.
Manually clean up the csv file in Excel, (this is by far easier to do now than later), you have to massage your fields to be compatible with your new PDA's file field strusture. (i.e. Cell Phone field becomes Mobile Phone field) and save the csv file in a format readable by Activesync. Probably csv again.
*** The following is how I do this, it's just a suggestion:
Backup your current files on your pda to an archive.
Erase your pda contacts folder.
Import the csv file into activesync and hotsync the pda.
Import your archive file into your pda using a manual choice for duplicate entries.
***
The following link has better info, but is not the one I've used in the past:
http://www.filesaveas.com/pdaconvert.html
Second option is to transfer all data to MS Outlook, (not outlook Express!), (not MS Outlook running business contact manager!) to a file that has the correct fields for your new pda already, and remap the imported data fields. save the file as csv, move it to activesync.