Here’s how to change the drive letter assigned to your USB drive.
1) Go to Start> Run and type compmgmt.msc:
2) Choose “Disk Management”:
3) Right-click on your USB drive, select “Change Drive Letter and Paths”
4) Click “Edit”:
5) Choose the drive letter among those available and click OK:
Note: Norton Antivirus, for some reason, has a tendency to balk when you change a drive letter (with some versions, the oldest, it was downright impossible). The easy solution is to disable it at that time, or, better yet, to change antivirus .