suppose if you have K: drive as you usb or pen drive here is steps to remove autorun.inf and be safe from usb virus.

start dos you will be in your home directory move to your usb drive by command below

c:\ k:

then use attrib command to list out all hidden/readonly/system files

k:\attrib

if you see autorun.inf with SHR attributes then virus exists in your usb drive.
a little explaination here is S for system file , H for Hidden file and R for readonly file.

virus make autorun.inf as an system readonly and hidden file so no one can see or delete it.

you need to remove these attributes from autorun.inf file by this command.

K:\attrib -H -R -S autorun.inf

now as these attributes are removed you can simple delete autorun.inf by del command.

k:\del autorun.inf

now you are safe. hAppY Safety :)