Cannot re-change my USB drive icon
I know how to change an icon on Mac. I changed the icon for my flash drive yesterday to a picture of Spiderman, and now I wish to change it to Captain America's Shield. But when I copy Cap's shield, and paste onto the flash drive, it pastes the Spiderman image!! Trust me Spiderman is NOT on the clipboard!
I noticed that I can paste the shield onto my 'Macintosh HD' which has never been changed before, but when I try pasting the shield onto my external hard drive, which has a custom icon, it doesn't work! I've even deleted the current icon, which resets it to the standard USB hard drive icon, and then paste the shield, but it pastes the old custom icon, which hasn't been on the clipboard since I first added it a year ago!!
I have even tried erasing the flash drive to no avail.
I have tried multiple methods of copying and pasting the icon, eg, copying the file, and opening in preview, selecting and copying...
What is going on and how can I change my drive icons??
Help much appreciated!
iMac, Mac OS X (10.6.8), iMac '07, Runs iTunes 11.3; Chrome