For starters, you need to scan your USB first using a virus scanner with an updated virus database (I recommend Avast or AVG). After being sure that your files aren't infected, you have to see if the virus hid your files or folders. Just go to your current window's Tools > Folder Options > View and check Show hidden files and folders.
You can try to Right Click and select Property for a particular file or folder and uncheck the Hidden attribute. But there are times when the check box is disabled.
When the Hidden attribute is disabled for your files or folders, follow these steps to unhide them all:
- Open the command prompt (Start > Run > type cmd and press Enter)
- On the command window type cd x: (where x is letter of your USB drive)
- Type in attrib /s /d -s -h *.* and press Enter
- Type exit and press Enter to close the command window
- attrib : allows change file/folder attributes.
- /s : includes subdirectories
- /d: include folders as well
- -s: clears system file attribute
- -h: clears hidden attibute