From Inflexpoint Technologies:
Proteg Manager allows you to convert a standard portable USB flash drive (USB storage device) into a security token, that can be used to securely access your PC. After installation you are prompted for a USB flash drive and can then select a user account that you want to protect. To access your PC with that account, you will need the created USB flash drive, as well as an additional password--you will always need both, the USB drive and the password. Version 3.3 adds new option that allows to disable lock screen when USB flash drive is disconnected.