Not sure of the answer to your format-disable question, but if the drive is a fixed drive / partition on your PC, you can remove the drive letter of the unmounted drive, using Computer Management -> Disk Management. Right-click on the unmounted drive, choose to change the drive letter, then click the 'Remove' button. This will stop it appearing in explorer or otherwise. If your encryption software supports mounting by device / partition instead of drive number (eg Truecrypt) this will work fine. You can always add the drive letter back again using the same option. From memory, it will work for removable drives also, though things may get funky if a different drive letter is assigned. I do this all the time for my Truecrypt partitions. I too would like to know how to disable format for individual drives SP