Deleting data from a USB memory stick

[Nick]

There are a number of possibilities here:

1. Its a rubbish drive
   
2. Its a Windows issue
   

Most likely, you are seeing a windows explorer caching issue - I don't know what version of Windows you are using, but XP certainly had an issue with Explorer caching directories but not re-syncing the cache with an external drive. i.e. when viewed from within Explorer the drive seems to have things on it that are not actually there. on the physical media..

The solution is to eject/dismount the USB stick (don't just unplug it). Then, once dismounted, re-insert the stick so it mounts again. This forces Explorer to reload its cache, and generally cures the issue.

Note that you may need to empty the recycle bin on the USB stick to actually free up space.

HTH

EDIT: Please note that this is not related to "wear levelling" or other h/w-type issues of NAND flash memory