Autorun is the most likely way to infect your computer. To prevent this we can disable autorun feature in Windows.
Press Start button ->Run.
In window that has appear type gpedit.msc and press OK button.

At the left part of "Group policy" window select "Computer configuration"->"System". Select "Turn off Autoplay" at the left part of screen when "System" is select.

Double click on "Turn off Autoplay". Point to "Autoplay" and in the drop-down list select "All drives".
Press "Apply" and "OK" buttons.