Trying out new operating system? I was trying Google Chromium OS, after the test, I tried to format my USB flash drive but surprisingly the USB drive was completely destroyed and had only 1GB usable space and other 3GB space was not there.

How to repair corrupt usb flash drive. Merge, create, repair partitions.

Normal formatting by Windows, does not recover anything. The Windows device manager / Disk management, there were around 8 partitions and only one partition was detectable by Windows which was 1GB. All other portions were of no any use.

Many attempts to recover deleted portions failed. Using may specialize applications but no use and the one that was perfect was a very tiny but a powerful tool 'BOOTICE'.

If you ever try the Chromium operating system on your PC, this tool will help you to recover your USB drive.
If you have the same problem and none of the partition is detected by Windows device management utility, try these steps.
Go to 'Physical disk' tab >> Parts Manage >> Re-partitioning >> USB HDD mode (single partition ). Click OK and format the drive.
This should format all the partition and create a single usable partition as normal USB flash drive.

If that fail, you can try USB FDD mode with no partition table.
If still you can recover the drive, keep trying other options.
Not only USB drive but the same applies to hard drives. It is a complete partition management utility plus a MBR and PBR processor plus image writer and many other useful features.
How To Repair Corrupt USB Drive, Merge And Create Partitions
Here is a quick list of features about what you can do with Bootice

Bootice is a free and very small tool / utility to manage, repair all types of memory devices like USB drive and hard disk.
How To Repair Corrupt USB Drive, Merge And Create Partitions
You can easily repair MBR / Master boot record or a memory drive like internal hard disk or a USB flash drive. Easily backup and restore the MBR into external file.
Bootice has also repaired PBR / Partition boot record. If you have multiple partitions on your hard disk, you can set the boot partition, same is the case with USB drive.
In my case, Parts manage feature of Bootice came to help. You can easily merge all the partitions of the USB drive or internal drive into one partition.
How To Repair Corrupt USB Drive, Merge And Create Partitions
You can format and create single or multiple partitions in a USB drive and use it as a multi partitioned hard drive.
Bootice also allows you to backup and restore partition table in a file.
You can easily activate, hide, delete, assign a drive letter or remove a drive letter to any partition or drive.
You can convert dynamic drive into simple or basic partition.
It can also format any specific part / partition of the drive.
If you have an ISO or IMG image of a CD, and have any problem with it Bootice can repair it.
If you have multiple operating systems installed on your hard drive and have problem in boot sequence or have problem dew to Grub, you can also repair GRUB.
It is really a must have utility that will surely help you one day.

check: http://www.olaintel.com/2017/12/how-to-repair-corrupt-usb-flash-drive.html for picture tutorial and dowload link