I have the new Treo 650 and am using Windows 2000. 

What I need is someone to help me figure out how to transfer and sync
my contacts and my calendar from Yahoo address book and calendar to
the Treo 650.

I've done it, but it's not pretty, with many duplicate contacts and no
easy way to delete them from the Treo.

I've also searched around using Google and there are some postings
scattered about tech forums, but I have not found a step by step
systematic explanation for how to do this easily.

For example, something that explains the proper "field mapping" of
contacts, and also explains how to set up weekly syncing.

So, if you can help, or can find help, the bounty is yours. Also
interested in any third party software that might aid me in this task.

Thanks for your help.

Dear 
"Intellisync for yahoo" can help you
download it at yahoo.
wish you good luck!