For backing up email, this is what I do (not sure if it's the "preferred" method, but it's what works for me):
Open Outlook (this is on 2003) > File > Import and Export > Export to file > Personal folder file (pst) > then select the folder/item you want to back up (inbox/read/sent/calendar/contact etc) > Next > I usually name them according to what they are, and the date I exported it (example: Outlook sent backup 6-21-08.pst) and save it wherever (my docs is good). Then, when you want to put them into the new install, use the same method, but choose File > import and export > import from another program or file > personal folder file (pst) then browse to the previous files you saved (might need to put them on a disc or thumb drive).
I've had to do numerous formats/reinstalls and this has always worked without issue.