Shares of the company fell 2 percent to $27.26 on Wednesday morning on the Nasdaq.
Seagate shipped 57.6 million hard drives during the quarter ended September 28, down from 66 million in the April-June quarter.
Seagate, along with rival Western Digital, has been struggling with weak PC sales in the United States and Europe, and increasing adoption of tablet devices.
Weak demand also enabled customers to get price cuts from Seagate, cutting into margins.
"Based on already-completed negotiations associated with the current quarter, we expect that ASPs (average selling prices) will decline about 5 percent (sequentially)," Seagate Chief Executive Steve Luczo said on a conference call.
Seagate forecast second-quarter revenue of $3.5 billion, below analysts' average estimate of $3.84 billion.
Earlier in October, Western Digital forecast current-quarter sales of between $3.55 billion and $3.7 billion, compared with estimates of $4.08 billion.
Windows 8, Microsoft's latest operating system launched last week, was expected to revive PC sales, but Seagate and Western Digital's weak forecasts have dispelled hopes of a year-end revival.
Seagate, whose hard disk drives (HDDs) and solid state drives (SSDs) are used to store data inside computers, has been depending on enterprise customers to keep its order book running.
However, in the first quarter, enterprise shipments fell to 6.3 million units, down 9 percent from a year earlier.
Seagate expects demand from enterprise customers to remain weak due to its high exposure to Europe. It also said tablets are likely to lengthen the refresh cycle for notebook computers.
First-quarter net income rose to $582 million, or $1.42 per share, from $140 million, or 32 cents per share, a year earlier.
Excluding one-time items, Seagate earned $1.45 per share. Revenue rose 33 percent to $3.73 billion.
Analysts were expecting earnings of $1.67 per share in profit on revenue of $3.75 billion, according to Thomson Reuters I/B/E/S.
© Thomson Reuters 2012
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