SECURITIES & EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13G UNDER THE SECURITIES EXCHANGE ACT OF 1934 (AMENDMENT NO. 1)* NAME OF ISSUER: QUANTUM CORP TITLE OF CLASS OF SECURITIES: QUANTUM CORP UNLESS OTHERWISE NOTED, THE SECURITY BEING REPORTED IS A COMMON STOCK CUSIP NO. 747906 20 4 FEE BEING PAID: NO (1) NAMES OF REPORTING PERSONS: J.P. MORGAN & CO. INCORPORATED S.S. OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS: 13-2625764 (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP: (A) (B) (3) SEC USE ONLY (4) CITIZENSHIP OR PLACE OF ORGANIZATION: UNITED STATES NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH: (5) SOLE POWER TO VOTE: 6,262,380 SHARES (6) SHARED POWER TO VOTE: 100 SHARES (7) SOLE POWER TO DISPOSE: 7,829,255 SHARES (8) SHARED POWER TO DISPOSE: 100 SHARES (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON: 7,931,055 SHARES (10) CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES: (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9): 4.9% (12) TYPE OF REPORTING PERSON: HC SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13G UNDER THE SECURITIES EXCHANGE ACT OF 1934 AMENDMENT NO: 1 DATE FEBRUARY 29, 2000 FEE BEING PAID: YES ITEM 1 (A) NAME OF ISSUER: QUANTUM CORP ITEM 1 (B) ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICES: 500 MCCARTHY BLVD MILPITAS, CA 95035 ITEM 2 (A) NAME OF PERSON FILING: J.P.MORGAN & CO. INCORPORATED ITEM 2 (B) ADDRESS OF PRINCIPAL BUSINESS OFFICE: 60 WALL STREET NEW YORK,N.Y. 10260 ITEM 2 (C) CITIZENSHIP UNITED STATES ITEM 2 (D) TITLE OF CLASS OF SECURITIES: QUANTUM CORP UNLESS OTHERWISE NOTED, SECURITY BEING REPORTED IS A COMMON STOCK. ITEM 2 (E) CUSIP NO: 747906 20 4 ITEM 3 TYPE OF PERSON: (G) PARENT HOLDING COMPANY IF THIS STATEMENT IS FILED PURSUANT TO RULE 13D-1 (b) CHECK THIS BOX (X) ITEM 4 (A) AMOUNT BENEFICIALLY OWNED: 7,931,055 SHARES, INCLUDING 0 SHARES WHERE THERE IS A RIGHT TO ACQUIRE. ITEM 4 (B) PERCENT OF CLASS: 4.9 ITEM 4 (C) (I) SOLE POWER TO VOTE: 6,262,380 SHARES (II) SHARED POWER TO VOTE: 100 SHARES (III) SOLE POWER TO DISPOSE: 7,829,255 SHARES (IV) SHARED POWER TO DISPOSE: 100 SHARES ITEM 5 OWNERSHIP OF 5 PERCENT OR LESS OF A CLASS: YES ITEM 6 OWNERSHIP OF MORE THAN 5 PERCENT ON BEHALF OF ANOTHER PERSON: VIRTUALLY ALL OF OUR ACCOUNTS INVOLVE OUTSIDE PERSONS WHO HAVE THE RIGHT TO RECEIVE OR DIRECT THE RECEIPT OF DIVIDENDS FROM,OR THE PROCEEDS FROM THE SALE OF, SECURITIES IN SUCH ACCOUNTS WITH RESPECT TO THE CLASS OF SECURITIES WHICH ARE THE SUBJECT OF THIS REPORT. HOWEVER, NO SUCH PERSON'S RIGHTS RELATE TO MORE THAN FIVE PERCENT OF THE CLASS UNLESS SUCH PERSON IS IDENTIFIED BELOW. ITEM 7 IDENTIFICATION AND CLASSIFICATION OF SUBSIDIARIES: MORGAN GUARANTY TRUST COMPANY OF NEW YORK - 3(B) BANK J.P. MORGAN INVESTMENT MANAGEMENT, INC. - 3(E) INVESTMENT ADVISOR J.P. MORGAN FLORIDA FEDERAL SAVINGS BANK - 3(E) INVESTMENT ADVISOR MORGAN TOYKO BANK ITEM 8 IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF THE GROUP NOT APPLICABLE ITEM 9 NOTICE OF DISSOLUTION OF THE GROUP: NOT APPLICABLE ITEM 10 CERTIFICATION: BY SIGNING BELOW I CERTIFY THAT, TO THE BEST OF MY KNOWLEDGE AND BELIEF, THE SECURITIES REFERRED TO ABOVE WERE NOT ACQUIRED AND ARE NOT HELD FOR THE PURPOSE OF OR WITH THE EFFECT OF CHANGING OR INFLUENCING THE CONTROL OF THE ISSUER OF THE SECURITIES AND WERE NOT ACQUIRED AND ARE NOT HELD IN CONNECTION WITH OR AS PARTICPANT IN ANY TRANSACTION HAVING THAT PURPOSE OR EFFECT. JAMES C.P. BERRY VICE PRESIDENT