Hewlett-Packard Co. shares plunged 20 percent to six-year lows today as investors reacted badly to the technology heavyweight’s bleak outlook and plans to spin off its PC business, FOXBusiness reported.

After declining more than 6 percent on Thursday, H-P was off another 20.26 percent this morning, easily making it the worst performer on the Dow Jones industrial average roster. The company alone erased 44 points from the benchmark index.

The dramatic selloff erased $12.5 billion from the Palo Alto, Calif., company’s market value.

A chorus of analysts downgraded H-P’s stock in response to the company’s downgraded outlook and plans to spin off its PC business and acquire information management company Autonomy Corp. for $10 billion.

H-P, which was the world’s largest tech company by revenue in 2010 and its biggest PC maker, projected 2011 earnings of $4.82 to $4.86 per share, compared with consensus calls for $5.01.