I have recently had this problem with my Cn 32GB memory device on Windows XP.
Thank to this and other forums I managed to reformat it as below:-
1. Open a DOS command window: Start>run and type cmd then click 'OK'
2. Type: format <drive>: where <drive> is the drive letter assigned to the memory stick shown in Windows Explorer.
3. At message: "Insert new disk ....." press 'Enter' key.
4. At message "Format cannot run because volume is in use ........ would you like to force a dismount on this volume? <Y/N>" press the 'Y' key.
USB devise will then be reformatted and usable in Windows XP.
I have trolled through this website looking for a solution and I finally found a way to keep my files so I wouldn't lose any of my data (I wasn't about to format my drive and lose 500gb of work)! I wrote up instructions of how I solved my problem here:
If the problem is persistent with the drive and you still can't copy files to it or format it after:-
1- You tried removing read-only permission from the drive properties
2- You tried formatting from Windows
3- You tried formatting from CMD using DISKPART
4- You tried editing the Registry solution (for WriteProtect word)
5- You tried the different free online tools like HDD LL Format tool and HP Format Tool
Then your drive is corrupt and needs the internal chipset S/W to be flashed, i.e. repairing the USB software. The steps below will lead you to get a small program to run on your USB memory-stick which is specific to your MANUFACTURER (make) and PRODUCT (model). If you don't want to go through the headache of the manufacturer's technical support then do it yourself as follows (which I source from here):-
1- Get Chip Genius portable application from here which you will use to find the VID and PID of the USB stick chip.
2- Search for the tool to repair your USB stick S/W from FlashBoot website . Search using your VID and PID from the previous step.
3- Search on Google for the name of the application you find in the "UTILS" column in the page from step 2 and the first link on Google Results (usually) will take you back to the FlashBoot website to download the utility to get your USB drive repaired.
It worked for me for my Kingston Data Traveler flash drive. It didn't work with all the common options for fixing the USB drive having "write protected", but the above solution I found after hours and hours of searching online and asking my computer-geeks colleagues.