Download h2testw:
h2testw.exe (click here to start downloading)
This file contains no viruses and other malicious software, which is proved by VirusTotal scanning results (go to virus scanning results page):

User guide for h2testw program:
1. Download and start h2testw.exe file (follow the above located link).
2. First of all, select the English language, it is in German on default, and one can understand nothing there:

3. After that, click “Select target” button in order to select a disk (an SD card, a flash-drive) for verification:

4. Select a disk, an SD card, a flash-drive:

5. Now click “Write + Verify” button and wait until verification is over:

“Writing” and “Verifying” columns must contain the same number of megabytes (the whole SD card or flash-drive size, if it was empty).
It’s recommended to use this program for verifying all the flash-drives, SD cards and disks after buying, especially if you buy them in China. Unfortunately, a level of fraudulence remains high among Chinese sellers. Far too often, they sell allegedly 128 gigabyte flash-drives, which prove to be 4 or 8 gigabyte ones.
If you have any questions left or need some details - please, ask a question!