To perform file recovery process on Android phone, both the internal memory and external memory of your Android phone should mount as drive letter when connected to the computer, and this can be achieved by enabling USB Mass Storage Mode on your Android phone.

However, most Android devices now use the Android 4.0 Ice Cream Sandwich and later version like Jeally Bean, which has brought fundamental changes to the file system. The USB Mass Storage Mode is replaced by mtp (media transfer protocol) and ptp (picture transfer protocol) mode, which has the advantages of safer removal, simultaneously accessing from both your computer and mobile device as standard USB storage, etc.

Therefore, if your phone runs OS version below Android 4.0 like Android 2.3 Gingerbread, you are fortunately enough to recover deleted/lost photos from both its internal memory and external memory with Photo Recovery software.

If you own a phone that has just upgraded from Android 2.3 to Android 4.0, like Samsung Galaxy S2, you still has the opportunity to recover lost by files by enabling USB Mass Storage Mode on your Phone with the following steps:
1.Go into “Settings>More>USB utilities” and then click “Connect Storage to PC”.
2. Plug one port of your USB cable into your Galaxy S2 and connect the other port to the computer.
3. The “USB connected” screen with a large green Android icon will appear, hit “Turn on USB storage”.
4. A confirmation dialog box will appear. Tap “OK”. Then the green Android icon will turn orange, indicating that the phone is now in USB Mass Storage mode. And your phone will appear as USB disk drives in “Devices with Removable Storage” and be assigned drive letters.

If you connect Android phones which runs 4.0 Ice Cream Sandwich or 4.1 Jeally Bean, like Samsung Galaxy S3 or Samsung Galaxy S4 directly to the computer, both the internal memory and external memory of the phone will not mount as drive letter and therefore can not be detected by the recovery software. The good news is that if you have wisely stored your deleted/lost photos on your phone external memory card, you still have the chance to restore them back with recovery software. Just take out your external memory out of the phone and insert it into a card reader and then connect the card reader to the computer. Almost all card readers will appear as a drive letter in “My Computer” of Windows when connected. So make sure get a large capacity external SD card to store all your important photos for your Android phones that runs Android 4.0 or above.