Remount

• If your card is not being recognized, you may simply need to remount it. This reestablishes the connection with the phone. Slide down the back cover and pull on the battery removal tab to lift the battery out. Push gently on the edge of the Micro SD card, and it will snap out. Push it back in until you hear a click, then replace the battery and cover.
  
  

Clean

• The gold-colored contacts on a Micro SD card should be clean and free of debris. Handle the card by the edges only, and never touch the contacts with your fingers. To increase the readability of the card, clean the contacts with rubbing alcohol and a cotton swab. Let it air dry completely before re-installing it to the Droid X.
  
  

Update Drivers

• If your Micro SD doesn't work when the phone is attached to a computer, you might need to update your USB drivers. Download the drivers for your device from Motorola.com, or install Motorola's "5.0 Driver with MotoHelper." The MotoHelper runs in the background, and it checks for driver updates each time your phone is connected by USB.
  
  

Format

• Formatting the card should be a last resort, as it will erase everything you have stored on it. If possible, use an SD card adapter to plug the MicroSD directly into the computer. Copy everything to the hard drive or another backup source. Remove the USB cable, then press "Menu" from the Home Screen. Press "Settings," then "SD Card & Phone Storage." Press "Unmount SD Card," then "Format SD Card." Touch it again to confirm.