Sounding like a guy starting to flex his activist shareholder muscles, Greenlight Capital chief David Einhorn, who made his bones shorting an under-capitalized, over-exposed Lehman months before its collapse, told an investment conference Wednesday that Microsoft CEO Steve Ballmer is stuck in a legacy time warp and has to go.

"His continued presence is the biggest overhang on Microsoft's stock," he said, pointing to his failure to deal with Google (whose stock seems to be seeking a new bottom itself these days), letting Apple get ahead of him, deals like Microsoft's $8.5 billion Skype deal and go-nowhere R&D.

When the news got out, Microsoft's usually sleepwalking stock rose.

In faulting Microsoft's "Charlie Brown management," Einhorn said what a lot of people have been thinking for a long time, but the chances of persuading Microsoft's board seems pretty hopeless. However, CNBC did report one of Microsoft's directors saying the issue could come up at the next board meeting the middle of next month.

Supposedly the board didn't fancy the Skype deal; only Bill Gates was able to persuade it so maybe Ballmer's out further on the proverbial limb than imagined.

Ballmer is Microsoft's second-biggest shareholder after Bill Gates with ~4% of the joint.

Einhorn's got about 0.11%, something like nine million shares. He could always form a unified front with other large investors.