Exporting your data essentially creates a back up of all current information found in your mailbox. it is also recommended check the size of your mailbox data.

If combine your data is close to 2gigs of information export only your emails to a .PST file and export calendar and contacts to a .CSV file. This will eliminate the possibility of corruption.

If you currently have a .PST you can simply import that file and all data will be uploaded to Outlook 2010.

Note; If your current .PST is a back up of a previous date it will only contain data up to that date stored.

hope this helps.