To manage the Microsoft Windows Backups you can use a command line tool.
Open a command prompt as administrator
Show the existing backup versions
Wbadmin get versions
Clean up the backup disk
To keep a number of latest backups and delete the rest
Wbadmin delete backup -keepversions:NUMBER_OF_BACKUPS_TO_KEEP
To keep the latest backup only
Wbadmin delete backup -keepversions:1
To delete all existing backups
Wbadmin delete backup -keepversions:0
