Do you frequently format and recover your computer? Does your computer goes slow, shutdown, and corrupt files? Don't blame your computer, previous user, or your USB's. It's the computer virus that multiplies and destroy files, folder, and programs of your computer. Though your computer was installed with different anti virus, anti spyware, and firewall, if you don't know how to manage and control them, they might still possibly affect your computer. Anti Virus must be updated daily, so their is a need to be connected to internet everyday or weekly, if you're not sure with USB's, before inserting it to your computer, have it scan first to a computer that had an updated anti virus.