Between Outlook Express and Hotmail: You can synchronize your local Outlook Express and Hotmail address books on Microsoft's server. First, set up Outlook Express to access your Hotmail account. Select Tools, Accounts and click Add, Mail to start the Internet Connection Wizard. Enter your Hotmail e-mail address in the top text box on the second page.
Once the account is set up, go to Outlook Express's address book and select Tools, Synchronize Now. If that option isn't there, select Tools, Options, check Do not share information..., and click OK twice. Exit both the address book and Outlook Express, and then reopen them. Now you can select Tools, Synchronize Now