The file formats are different... you probably won't have any luck going from the newer client to the older Outlook Express. Try installing Windows Live Mail... that would be your best bet... though I don't know if it works with 2K.
XP or Server 2003 would have been a much better choice if you didn't want Vista...
I have replaced Vista Ultimate with Windows 2000 Server ... on a HP m8120n, taking the easy way out and replacing the primary hard drive.
I can load the "Vista Drive" as a slave and move or copy files such as word documents but, is there a way to transfer the Address Book entries ... "Contact" files to either Outlook or Outlook Express?
The same question applies to the email messages themselves, though I don't know either the extensions or locations of those files.
I would disconnect the Win 2000 Server drive - power up and enter BIOS, change your bootable hard drive back to Vista (the slave drive) save changes and you should ! see Vista back. (Inncorrect bios entry may stop your computer !!)
Now copy your word documents on a USB memory stick(just in case !!), Open outlook xpress (offline) and copy address book - use import/export - Email Stoarge - and send/save in memory stick - you can also copy all your emails (file them in new folders for INBOX & SENT- and export them to memory stick - they will appear saved as .dbx files with no details -
Power off - connect Win 2000 Drive back, change in BIOS as bootable drive - power up - open outlook xpress - import the .dbx files from stick one at the time (inbox) (Sent) and place. You can also do the same to your address book.
One more tip - when saving your word files try to save them in an older version of word if you can - good luck !!