Quantum Corp. warned that sales and earnings for its fiscal fourth quarter will be lower than expected because of falling prices for desktop hard drives and weak demand for high-end tape drives. It said it expects break-even earnings, or slightly better, for the three months ending March 31. Sales are forecast to be 20% lower than the $1.52 billion reported in Quantum's third quarter. In the year-ago quarter, Milpitas-based Quantum reported earnings of $87.7 million, or 64 cents a share, on sales of $1.56 million. Other drive makers suffered in the December quarter, with Western Digital Corp. and Seagate Technology Inc. also posting poor performances. Quantum shares rose 31 cents to close at $20.50. Trading was halted on Nasdaq before the announcement.