Ensure that
Set Windows To Show Hidden Files and Folders
* Click Start.
* Open My Computer.
* Select the Tools menu and click Folder Options.
* Select the View Tab.
* Under the Hidden files and folders heading select Show hidden files and folders.
* Uncheck the Hide protected operating system files (recommended) option.
* Uncheck the Hide Extensions for known file types
* Click Yes to confirm.
* Click OK.
Now, with the Flash card in the external drive
Run Flash_Disinfector.exe again
Afterwards, when you open your Flash drive thru MyComputer
You should see the Auto.inf folder
Inside that folder, you should see a file created by Flash Disinfector, leave the folder/file alone
It will help from future infections
Remove that flash card, insert another and again run Flash_Disinfector
Besides the Autorun.inf folder we're creating, do you see any other files on the Flash drives with autorun.inf names?
Ensure to Scan each drive with Avast, ensure avast is right up to date