While importing .pst files from external devices in Outlook 2010, you see the error message "You may not use the file. There is not enough permission to use pst files". You may not use the file. There is not enough permission to use pst files.
This error can occur when importing .pst files from an external device in Windows 7 that have been exported from Windows XP to the external device. The cause of this issue could be that the user accounts for Windows XP and Windows 7 were incompatible or that the account control had not been set properly.
Set the permission as "Everyone" on the .pst files for import
Right click the .pst file you are about to import and click Property. In this article, backup.pst was used for .pst file as an example.
In the backup.pst property screen, click Security, and then Edit.
In the backup.pst permission screen, click Add.
In the Select user, computer, service account or group screen, enter Everyone and then click Confirm.
In both the backup.pst permission and backup.pst property screen, click Confirm.
Import the .pst file back to see if the issue has been resolved.