You can select and customize the System Cleaner and Optimizer search to specific drives. You can do this by pressing the Options -> Drives from the main Window of System Cleaner and Optimizer. There you will see all the drives on your System with there Volume Name, with a check box besides them.
When System Cleaner and Optimizer is run for the first time it by default selects all the drives on your system excluding Floppy Drive and read only Drives such as CD Rom drive.
To include a drive in search process just press the Check box beside the Drive Name. To exclude the drive from the search process just uncheck the list box.