If you are sure that your computer is not infected and you have a virus in your USB and want to delete it manually
GOTO Folder options
in "VIEW" tab goto "hide Protected operating system files"
By unselecting it and "show all files and folders" You will be able to view system files
just open your USB drive by EXPLORER BUTTON Do not double click it
You Can clearly see the file with .exe extension
Delete autorun.inf and virusname.exe files and now VIRUS HAS BEEN REMOVED
before do that,
you must Disabled Autoplay,
Run - Gpedit.msc - Computer Configuration - Adminstrative Template - System - Double Click Turn off Autoplay - Choose Enabled - Turn off Autoplay on : All Drives
if you're not disabled autoplay, you can't delete virus,
and maybe virus disable Folder Options too..