The elimination of Movie Gallery and Hollywood Video as Blockbuster's competitors and the agreement by the major studios to allow their movies to be rented at its stores and via its direct-mail unit have failed to halt Blockbuster's tumbling share value. After rising last month on word of the rivals' demise and the studios' assurances, the company's stock fell to an all-time low of 21 cents on Monday as shareholders began dumping the stock amid reports that the company plans to seek so-called debtor-in-possession funding from bondholders and that it is in talks with them to convert at least a major portion of its $900-million debt into equity. Some analysts predicted that the effort would fail and that it was only a matter of time before Blockbuster would be forced into bankruptcy.