I'm going to format my HD. But i want to know is can I backup my emails address book etc before i do this?

Presuming your actually talking about Outlook and not Outlook Express -

File > Import and Export > "Export to a file" > Personal Folder File (.pst) > Click Personal Folders at the top of the list and then check the Include Subfolders option > Choose a location to save the file and click finish.

Selecting all the subfolders under the Personal Folders will backup everything, Inbox, Outbox, Sent Items, Calender, Notes etc. If you only want your Inbox, purely select that folder.

If you are using outlook you don't need to export. Just find the .pst file you are using & copy it.