If your phone has BT you can just send the contacts directly to your N800. I've done that several times with my S-E phones. It'll end up as a VCARD file, at least if you send contacts from an S-E phone or a Palm PDA.

With my S-E k700i I do the following:
1) Turn on BT on the N800
2) Set it to visible
3) On the phone, select Phonebook
4) Options->Advanced->Send all contacts
5) Select Via Bluetooth
It'll search for and find the N800. Select it and send.
6) A pop-up should show up on the N800, with the suggested name to save.

Doing that I got a file "Whole Phonebook.vcf" in MyDocs/.documents/ on my N800.