If you receive many alerts from your antivirus program that an "autorun.exe" virus has been found, this may be a fake alert. It may be a virus, or maybe not.
To get rid of this alerts you can simply automatically disable all autorun processes for your USB drives.
I recommend you to use Bitdefender USB Immunizer which is free.
Install it and run the .exe file.
Click on the icon from the middle of the application (plug-in USB drive to your computer first).
In a few seconds your USB will be immunized and the autorun.exe file will be quiet.
No more problems with this kind of alert.