I always prepare these USB Keys running Linux....
Maybe the process started...on your pc...and You cannot remove because You was Slurping your own data...
Not sure about that,but I always do this in Linux.
;)
U3 works having usb key formatted in 2 partitions.....and the second acting as disk
IF i make 2 partitions on my usbkey...setting the bit of the second as a disk
It can work?
Any tests ?