By default, PerfectDisk 2008 does not display drives connected by USB, firewire or external connections. Even though these devices represent themselves as a fixed hard drive, they may not support defragmentation. Prior to defragmenting these dvices, you'll need to check with the device manufacturer and verify that defragmentation is supported on these devices.
If your device does support defragmentation, then you can enable USB support in PerfectDisk 2008 by going to the PerfectDisk settings tab, removable storage and select the option to allow optimization of USB and firewire connected drives and click ok.For Flash drives, check the option to allow defragmenting flash drives. The device will display once this option is enabled.
Defrag your tunes.