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NEW YORK ( TheStreet) -- If a company's fundamentals are declining, don't think they can be turned around easily, Jim Cramer said on "Mad Money" Tuesday. He reminded investors one of the time-honored investing mistakes and the biggest personal portfolio management errors they can make is to believe in a turnaround or takeover. Case in point, Hewlett-Packard ( HPQ) and Best Buy ( BBY), two stocks that were down 11% and 13%, respectively. Cramer said investors may be tempted to buy into these companies because they're both household names. Surely they'll be able to resurrect themselves, many may think, but in reality both stocks are total disasters. Tuesday, HP announced a $5.5 billion write-down for its purchase last year of the U.K.-based Autonomy. According to the company there was widespread accounting errors and misrepresentations at Autonomy, which caused HP to lose nearly $8.8 billion of its $11 billion investment. Cramer said the problem with HP is it's no longer an innovator but an assembler of products that are in decline. PCs are losing out to tablets while margins are shrinking in the printer business. Meanwhile, rivals are eating HP's lunch in the consulting business. Cramer said it's not too late to sell this stock, which has already lost 55% of its value this year. Then there's Best Buy, which reported more disappointing results Tuesday and continues to hope that someone, perhaps its founder, will swoop in and take over the company. Cramer reminded investors the tech world is littered with turnarounds and takeovers that never happened. Remember Circuit City? How about Radio Shack ( RSH)? That company is on death's door. Cramer said the list of tech stocks that are hoping for a turn is a long one that includes Nokia ( NOK), Research In Motion ( RIMM), Dell ( DELL) and even Microsoft ( MSFT). In all of these cases the fundamentals are in decline and management may be able to do little to stem the losses.