Download TRUE CRYPT
Start with an empty Flash Drive. Download and install TrueCrypt from.
Click 'create volume' to create a standard TrueCrypt volume. Click 'select device' - choose your USB flash drive, click it, then choose OK.
Click 'next' to see the encryption options (algorithms) you can use, click 'next' to accept the volume size, then enter a password.
Move your mouse over the 'next dialogue' to set a random starting point for the TrueCrypt encryption, then click 'format' to format the flash drive.
To access the Flash Drive click 'select device' in TrueCrypt and chose the flash drive. Select 'mount' enter your password and the Flash Drive will now appear in explorer Click 'dismount' to remove the drive.