|It sounds to me like that presentation of your classmate has a virus on it. Try scanning the usb stick with a virusscanner, also make sure your computer does not have any virusses. |
Also try to minimize the amount of time you spent on the computer. You cant get your files back if they are physically overwritten.
after that you can try and get the files back with a copy of getdataback which is available on the internet. this program searches your harddrive for everything that was ever delete and can get it back for you unless it has been overwritten by something else.
You can always, if all hope is lost, reinstall your machine and format the usb stick if all else fails ofcourse.