On Page 509 of the Backup Exec 2010 Administrators Guide for BE 2010 http://www.symantec.com/docs/DOC2211 this can be found :
Deleting a backup-to-disk file
You must movebackup-to-diskfilestothe RetiredMediasetbeforeyou can delete
them. When you delete a backup-to-disk file from the Media tab in Backup Exec,
it is deleted from Backup Exec but the Windows folder and files still exist in
Windows Explorer. You can recreate the deleted backup-to-disk files.
If you want to delete the file from the disk, use Windows Explorer to navigate to
the file and delete it. When the file is removed from the disk using Windows
Explorer, you cannot restore it in Backup Exec.
To delete a backup-to-disk file
1 On the navigation bar, click Media.
2 Click the media set that contains the backup-to-disk file.
3 Use the Windows drag-and-drop feature to move thebackup-to-diskfile into
the Retired Media set.
4 On the results pane, select the backup-to-disk file you want to delete.
5 Under General Tasks in the task pane, select Delete.
6 When prompted to delete thebackup-to-diskfile,