5. A storage medium having stored thereon a computer program executable by a computer to perform a process comprising the steps of: acquiring one or more distributed keywords; determining an importance level of each keyword acquired in the acquisition step, wherein, when the respective keyword is registered, the importance level is calculated by subtracting a time difference value from a number of occurrences of the respective keyword, in which the time difference value is equal to a predetermined value times a difference between a current time and a last acquisition time of the respective keyword, and wherein, when a result of subtracting the time difference value from the number of occurrences of the respective keyword is negative, the importance level of the respective keyword is set to zero, and wherein, when the respective keyword is not registered, the importance level of the respective keyword is set to one; extracting text information of a subtitle included in a program; performing morphological analysis on the text information of the subtitle; comparing each keyword acquired in the acquisition step with each keyword detected via the morphological analysis performed in the subtitle morphological analysis step; recording the program if the comparison performed in the comparison step indicates that any keyword acquired in acquisition step is identical to any keyword detected via the morphological analysis performed in the subtitle morphological analysis step; and registering, in a table, the program recorded by the recoding step and information indicating the importance level in association with the keyword.
5. A storage medium having stored thereon a computer program executable by a computer to perform a process comprising the steps of: acquiring one or more distributed keywords; determining an importance level of each keyword acquired in the acquisition step, wherein, when the respective keyword is registered, the importance level is calculated by subtracting a time difference value from a number of occurrences of the respective keyword, in which the time difference value is equal to a predetermined value times a difference between a current time and a last acquisition time of the respective keyword, and wherein, when a result of subtracting the time difference value from the number of occurrences of the respective keyword is negative, the importance level of the respective keyword is set to zero, and wherein, when the respective keyword is not registered, the importance level of the respective keyword is set to one; extracting text information of a subtitle included in a program; performing morphological analysis on the text information of the subtitle; comparing each keyword acquired in the acquisition step with each keyword detected via the morphological analysis performed in the subtitle morphological analysis step; recording the program if the comparison performed in the comparison step indicates that any keyword acquired in acquisition step is identical to any keyword detected via the morphological analysis performed in the subtitle morphological analysis step; and registering, in a table, the program recorded by the recoding step and information indicating the importance level in association with the keyword. 9. The storage medium according to claim 5 , in which the predetermined value is 0.5.