USB flash drive and all types of Flash Cards (SmartMedia =SM card, Compact Flash = CF card, MultiMediaCard = MMC card, Secure Digital = SD card, Memory Stick) have long been used on a large scale and widely available, but they have some other applications besides being storage devices. For example: As a boot disk for Windows PE OS, as a system installation disk, as a replacement for various Live CDs, and so forth. Today we are going to talk about using USB flash drive (Flash Card needs to cooperate with the card reader to work the same way) as a key for locking/unlocking your computer with ease.