Minneapolis ? Best Buy Co. Inc. offered voluntary severance packages to virtually all its 4,000 corporate employees Tuesday as the nation’s largest consumer electronics chain announced its third-quarter profit skidded 77 percent.

The results — which beat Wall Street’s lowered expectations — came in what the company called the “most challenging consumer environment” in its history, an environment so rough Best Buy hasn’t been able to take full advantage of the bankruptcy of its largest rival, Circuit City.