As a hedge-fund superstar, Greenlight Capital's David Einhorn makes moves that are worth watching. It's about that time of year when quarterly 13-F SEC filings, which disclose the positions the fund is holding, are starting to roll in. Let's take a look at some of the notable changes in Greenlight's portfolio over the past few months to get an insight into what this value investor has his eyes on.

Increased position: Apple
During the fourth quarter, Greenlight increased its position in Apple (Nasdaq: AAPL) from about 1.31 million shares to over 1.46 million shares, a roughly 11% increase in position size. This was also the quarter where Apple lost Steve Jobs, launched the iPhone 4S, and put up a surprise earnings miss relative to Wall Street expectations.

With Apple's most recent quarter obliterating everyone's expectations and the subsequent rally to new heights -- shares recently topping $500 for the first time ever -- you can bet Einhorn is pretty pleased with this move.

New position: OmniVision
As a shareholder, I've always had mixed feelings about image-sensor specialist OmniVision Technologies (Nasdaq: OVTI), but even in my darkest bouts of backside-illuminated depression, one fact has remained inescapable: OmniVision is ridiculously cheap. As of its most recent quarter, the company was sitting on $7.79 per share in cash and short-term investments alone.

That rock-bottom valuation has evidently attracted Einhorn's attention with a new, small position of nearly 197,000 shares. While my personal position currently sits next to a lot of red ink, it does give me a little more confidence to know that Einhorn is on my side.

New position: Research In Motion
This one was a downright shocker to me, but evidently Einhorn is bottom-fishing by picking up a new position in Research In Motion (Nasdaq: RIMM). RIM had an awful year by just about any measure you can think of, the most glaring of which was its share price shedding over three-quarters of its value.

Greenlight's 2.9 million RIM shares were added in the fourth quarter, so the loss on the position presumably shouldn't be too large. The position is surely sitting at a loss right now since shares are currently below $15, lower than any time in 2011. Since the turn of the year, RIM has had a bit of a shakeup, naming a new CEO and chairwoman with high hopes of a turnaround.

RIM sports a P/E under 4, which is bound to attract the value gurus, but I'm going to have to officially disagree on this one. Research In Motion isn't a value buy -- it's a value trap.

New position: Yahoo!
Speaking of upper-level shakeups, that brings us to Yahoo! (Nasdaq: YHOO). During the tail end of last year, the purple portal gave its foul-mouthed CEO Carol Bartz the boot -- over the phone, no less. The company remained without a permanent head throughout the rest of the year, with CFO Tim Morse acting as interim CEO.

It was against this backdrop that Greenlight picked up just over 3 million shares of Yahoo!. Just after the turn of the year, Yahoo! named a new CEO, Scott Thompson, who had previously led eBay's PayPal. Shortly after, co-founder and ex-CEO Jerry Yang called it quits. Rumors resurfaced late last year that Microsoft was interested in Yahoo! again, four years after Yang spurned Mr. Softy's previous advances – and whose $33 per-share offer looks dreamy compared to today's $15 price.

With Yang out of the way, who knows? Maybe Microsoft will come back to the bidding table, which would certainly delight Einhorn, since Greenlight's unchanged Microsoft position continues to irk him to no end.

New position: Dell
Also on the new tech position list is No. 2 domestic PC maker Dell (Nasdaq: DELL). Greenlight opened a 14.1 million share position on the computer vendor at a time when Dell was trying to capitalize on domestic PC top dog Hewlett-Packard's identity crisis.

Meanwhile, Dell has yet to formulate a meaningful game plan with the biggest revolution in computing in generations, the mobile revolution. Dell's attempts at smartphones and tablets have been met with commercial failure, most recently with both the Streak 5 and Streak 7 devices.

That being said, this trade is working out for Einhorn with Dell enjoying gains around 23% year-to-date and prices higher than any seen in the fourth quarter.

Tech time?
Einhorn's tech moves look awfully prescient, considering that the Nasdaq Composite is up roughly 12% so far this year, outperforming the Dow Jones Industrial Average and S&P 500, whose 5% and 7% respective gains pale in comparison. But then again, as a relatively tech-centric investor myself, I can't say I'm complaining.

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