Why does a USB drive lose space?
The lost space on a USB drive often occurs after trying to burn a system to the USB drive. Some operating system (OS), such as Chrome OS and Linux, will change the partition system of your removable device, so there will be little free space on your USB drive. Using some third party software inappropriately or an unsuccessful formatting may also cause inaccessible portion on your USB drive, which is shown as unallocated space.
A method of getting back this unallocated space to use Disk Part which is a utility built into Windows within the command line.
Warning: DISKPART is dangerous – do not use if you don’t feel comfortable with it! Insert your USB disk, make sure it is recognized by Windows (with the lower capacity), and then do the following:
1) Type “DISKPART” from the Command Prompt (accessible by clicking on Start and then typing “cmd” into the open field); you will then see the following prompt: DISKPART>
2) Type “LIST DISK” to see what number your USB drive is listed as.
3) Type “SELECT DISK 2” (if your USB is disk 2; replace # with your disk #); Diskpart will confirm that “Disk 2 is now the select disk.”
4) Type “SELECT PARTITION 1” (this command selects what should be the only partition on your USB drive, the small one that you want to delete to get back the larger, full partition size). Diskpart will confirm with “Partition 1 is now the selected partition.”
5) Type “DELETE PARTITION”. This will delete the old partition. There are no warning prompts if you have existing data – make sure you have copied everything off before doing this!
6) Type “CREATE PARTITION PRIMARY” to create a new, full-size partition. Diskpart will confirm with a message of “Diskpart succeeded in creating the specified partition.” You can type in “LIST PARTITION” to confirm the new, full-size.
7) Type “EXIT” to leave Diskpart. You can now format your USB drive by using the standard Windows formatting process.
There are also other third party tools available, you can find some of them at the link below or check out the downloads section.