How to backup of Outlook in case of formatting Hard disk Drive?

In case of formatting HDD, the main part is to take the backup of mails means outlook we are taking backup of mails which are saved in PST (means in local computer or server) PST saved in the profile of the user means proper destination C :/> documents & settings\user name\windows\microsft\outlook in that in some folder or if the user save in her own destinations in C drive or D drive So, we have to take the backup of PST.