In order to backup your mail, contacts and calendars you must create a PST file. Open Outlook and select File > Import > Export. From the list of options select Export to a File. Then select the PST option:
Select your inbox and create the file for it. It is recommended that you save the PST backup to an external hard drive:
After you create the PST file for your mail, you will need to repeat this process for your contacts and calendars. Use the same steps but instead of selecting your Inbox, select contacts then another backup for calendars.
We also recommend other normal system backup that should already be in place. Things such as documents, media and anything else you do not want to lose should be backed up prior to installing.