Just to clarify, when you perform a backup using the THREADCOUNT option, the backup is internally performed using 'multiple DISK options' as done for native SQL Server backups, but instead of writing the output to multiple files, SQL Backup consolidates the data and writes it out to a single file.
That is why when you converted the SQL Backup file to native format, 3 files were generated as what is what SQL Server requires in order to perform the restore.
SQL Backup Consultant Developer
Associate, Yohz SoftwareBeyond compression
- SQL Backup goodies under the hood, updated for version 8