You have got a virus in your flash drive and/or your computer.
Login to your system in safe mode.
Then do a full antivirus scan of your system.
You should be able to delete your files in safe mode if the virus is not active. If you have any file with *. vxd extension delete it. Also try deleting autoexec.bat and any .ini files present.
If this doesnt help then formatting is always the last option.