I purchased a 64gb Centon DataStick Sport. I received an error message saying that it is write protected about halfway into a data transfer. It does not show up under My Computer but when I go to disk management it shows up as USB Mass Storage Device under Disk 1, unknown, 59.8 GB, Not intialized. There is no drive letter. I tried using "cmd"->diskpart->list disk->select disk 1->clean but that didn't work. When I used select disk 1->detail disk, it would crash. When I entered clean all, it would bring up that it was write protected. Today was the first time I've ever used the cmd prompt so I'm unsure of what to do next. I can't format it using format e: because there's no drive letter assigned.
More about :usb flash drive write protected shows unknown disk management
The other thing that I usually try in Windows 7 (assuming the drive does not have a physical lock and if a flash drive it is not really old and worn out preventing further writes) is to set the Win 7 registry key to allow writes.
Login as an administrator on the computer. Open regedit.exe by typing that in the start search box. Navigate to this key:
You might need to create the key StorageDevicePolicies if it does not exist yet.
Select the StorageDevicePolicies key with a right-click into the right window.
Select New > Dword (32-bit) Value from the menu and name the new entry WriteProtect.
Double-click the new WriteProtect key and change the value to 0. If you want it to be read only you can change it back to a value of 1.
Save the key changes by clicking OK after each.
Restart your computer and then attach and test the USB device.