Updating and restoration method of system file

In a computer system wherein operating systems each having a file replacing function are stored in a first memory area and a second memory area, respectively, and further, a plurality of system files which are access-locked by said operating system of the first memory area during operation thereof are stored in said first memory area, a system file updating and restoration method of performing updating and restoration of said plurality of system files by software characterized in that said software includes:

• a step of terminating the operating system in operation of the first memory area and activating the operating system of the second memory area;
• a step of replacing the plurality of system files in said first memory area with substitute files prepared in advance by using the file replacing function of the activated operating system of the second memory area and preparing backup files of the replaced system files;
• a step of determining whether or not said file replacement is finished normally and restoring said backup files in said first memory area when not finished normally;
• and
• a step of terminating the operating system in operation of the second memory area and activating the operating system of the first memory area when said file replacement is finished normally or when the restoration of said backup files is finished.