Abstract: A CD-ROM is recorded with a CD-ROM effective period and an effective period of a content stored in the CD-ROM. A CD-ROM effective period judging section of a personal computer reads the effective periods, compares these periods with a machine date generated by a machine date generating section and enables a purchase slip transmitting section to transmit a purchase slip only when the machine data falls within the effective periods. A CD-ROM effective period judging section of a center compares the present date with the CD-ROM effective period and the content effective period registered on a goods master, reads the key from the goods master and transmits the key to the personal computer only when both of a CD-ROM number and a content ID written onto the received purchase slip fall within the effective periods.

Abstract: A CD-ROM is recorded with a CD-ROM effective period and an effective period of a content stored in the CD-ROM. A CD-ROM effective period judging section of a personal computer reads the effective periods, compares these periods with a machine date generated by a machine date generating section and enables a purchase slip transmitting section to transmit a purchase slip only when the machine data falls within the effective periods. A CD-ROM effective period judging section of a center compares the present date with the CD-ROM effective period and the content effective period registered on a goods master, reads the key from the goods master and transmits the key to the personal computer only when both of a CD-ROM number and a content ID written onto the received purchase slip fall within the effective periods.

Abstract: A goods master is stored with sales prices and sales effective periods of respective contents. A contract master is stored with data as to whether the sales price can be reduced. A key sales section charges a content purchaser for the sale price stored in the goods master. An updating section compares the present time with a sales effective period recorded on the goods master and reduces the sales price recorded on the goods master as far as the contract master is recorded with data indicating that the sales price can be reduced for a content with a remainder of the sales effective period being one month or less.

Abstract: A content proceeds distribution system distributes proceeds of a sold content to third parties. Each of the third parties has a right of charge, not prescribed in a sales contract, at a rate corresponding to the right thereof. A content database stores by content IDs all providers of the content and all the parties having the right of charge for copying and selling the content. An agreement of a share allocated to an operator of an SD center is registered in a contract master. A payment section, upon a payment of proceeds, subtracts the share of the operator of the SD center from the proceeds by referring to the agreement of the share of the operator that is registered in the contract master. The payment section next distributes the proceeds after subtraction according to each ID stored in the content database.