How to Unmount an SD Card on a Droid
Most Android cell phones feature a MicroSD card slot for expandable storage. The MicroSD card is the primary storage for music, videos, pictures and secondary app files. If you want to remove the SD card from a Droid phone, it's best to unmount the card from the software before physically removing it. The "soft" unmount is relatively simple, but can be hard to find for inexperienced Android user.
Unmounting in Android software
Turn on your phone and swipe the unlock tab to the left. Press the "HOME" button.
Press the "MENU" button, then tap "Settings." Scroll down to the bottom of the list and ta[ "SD card & phone storage."
Tap "Unmount SD card." The card is now ready for physical removal -- if you need to access the card again, tap "Mount SD card."
Removing SD card
Press the "Power" button to put the phone in sleep mode -- you don't need to turn it off. Turn the phone over so that the back is facing you.
Slide the battery cover up and remove it. Set the cover aside. Slide the SD card out of the slot, being careful not to jostle the battery. Note: on some phone models this card is physically underneath the battery, so you may need to power down the phone.
Replace the battery cover and snap it tightly into place.