Apple Computer

(AAPL) - Get Apple Inc. (AAPL) Report

fell 4.2% in preopen


trading Friday morning. After the company warned that fourth-quarter earnings would be just 30 to 33 cents per share, below the Street estimate of 45 cents Thursday, Apple's shares plunged 46% in after-hours trading.

The company blamed lower-than-expected sales of its new

Power Mac G4 Cube

, lower September sales in all regions and slower educational sales.

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Bear Stearns

lowered its ratings of the entire PC sector, and tech stocks were broadly lower in the preopen.


(DELL) - Get Dell Technologies Inc Class C Report

was down 5.4% and

Cisco Systems

(CSCO) - Get Cisco Systems, Inc. Report

fell 3.3%.