Slammed by "seismic changes in consumer behavior," Best Buy (BBY) slashed its full-year earnings guidance and warned of even steeper sales declines. 

The gloomy outlook from Best Buy comes just days after fellow electronics retailer Circuit City (CC) filed for bankruptcy protection, becoming the largest retailer this year to go under. 

“Since mid-September, rapid, seismic changes in consumer behavior have created the most difficult climate we’ve ever seen. Best Buy simply can’t adjust fast enough to maintain our earnings momentum for this year,” CEO Brad Anderson said in a statement. 

Shares of Best Buy fell double-digit percentages in premarket trading. 

The electronics retailer also reported a 7.6% slide in October same-store sales following a modest decline the month before. Best Buy sees sales potentially plunging even further over the next four months, forecasting declines of 5% to 15%.

Best Buy now expects fiscal 2009 earnings per share in the range of $2.30 to $2.90 per share, down from its earlier forecast of $3.25 to $3.40 per share. The midpoint of that forecast represents a 17% decline from earnings per share of $3.12 in fiscal 2008.

The company broadened its fiscal 2009 revenue forecast to $43.7 billion to $45.5 billion. 

“In 42 years of retailing, we’ve never seen such difficult times for the consumer. People are making dramatic changes in how much they spend, and we’re not immune from those forces. That’s why it’s critical that we manage our spending, while preserving key growth initiatives. Having said that, we believe that our strategic indicators remain strong," Chief Operating Officer Brian Dunn said in a statement. 

On top of the problems in the credit markets and weak overall economy, Best Buy blamed the stronger U.S. dollar for its lowered guidance. 

Additionally, Best Buy warned it plans to end the third quarter with higher-than-expected inventory levels, short-term borrowings and accounts payable.

However, the company said it is "proactively working with its vendors to adjust both its inventory levels and its near-term working capital position." 

The biggest change to its capital position comes from a new, $150 million "committed U.S. credit facility" that is aimed at providing extra liquidity to address the current climate and "potential opportunities," Best Buy said. 

The company said the new facility expires on December 17 and is partly in response to the bankruptcy of one of the participants in Best Buy's existing $2.5 billion line of credit.