Abstract: A method for limiting the number of times that software can be installed on different computers is provided. The method is suitable for PC with disk ROMs. With the USB flash drive connected to PC, the method includes the steps of: (a) the CD in the Disk ROM starting the software installation process; (b) the installation process requesting a hardware identification from the PC; (c) comparing the hardware identification of USB flash drive to determine if continuing the software installation process; (d) decoding the identification file in the USB flash drive; (e) checking if the hardware identification being already stored in decoded identification file; and (f) determining if finishing the software installation process in response to the checking step.