In this series, we take a look at the 25 stocks on the S&P 500 Index (SPX) that have turned in the worst performance during the past decade -- what went wrong, and what happens next.

In my day job, analyzing equities for Schaeffer's Investment Research, I'm always focused on one metric: expectations. They're not always easy to quantify, but investors' and analysts' expectations for a stock more often than not tend to drive its performance. For example, widespread skepticism makes it that much easier for a company's stock to bounce in the event of a positive development. And, on the other side of the coin, we have Unisys Corporation (NYSE: UIS) as a cautionary tale.

What went wrong? At number 7 on our list of SPX losers, UIS lost 86% of its value during the 10-year period that ended June 30, 2008. The shares peaked at $49.69 in September 1999, narrowly exceeding their previous high in October 1987. Shortly after tapping this all-time peak, Unisys would learn a harsh lesson about the danger of high hopes.

In the company's third-quarter earnings report, which hit the Street in October 1999, UIS admitted that revenue grew by just 4%, falling well short of analysts' expectations for an increase of 11% to 12%. Disappointed investors sent the shares plunging 37% over the course of one session, a sharp sell-off that surprised more than a few stock-market veterans. But, as Merrill Lynch analyst Steven Milunovich explained to The New York Times, "This company, under Larry Weinbach, has done nothing but meet and beat expectations. So when they disappoint, it makes it that much worse."

For investors, the hardest question often faced is when to sell a stock. Even when a stock issues a profit warning, if you are a long-term investor, that doesn't always justify one to pull the trigger.

There is no question it's easier to buy a stock than to sell. With that being said, today I was faced with an easy call. I call it the "three strikes and you are out" policy. If a company disappoints me three times in the span of six months, you're out (How long until pitchers and catchers report to spring training?).

Retalix (NASDAQ: RTLX) the Israeli provider of software solutions to retailers and distributors, today announced that it was going to miss its earnings estimates for the quarter. This is not the first time this has happened -- last quarter the same thing happened.

Earnings season has claimed its most recent victim, this time it is Capital One Financial (NYSE: COF) that is feeling the pain following a weak first quarter earnings report.

The Virginia based company reported that their first quarter earnings sank 24% and were forced to lower their 2007 forecast. For the quarter the company reported earnings per share of $1.62 on $3.43 billion. Analysts had been expecting the company to show $1.98 per share with revenues of $4.1 billion.

As if the quarterly miss wasn't bad enough the company also was forced to lower their estimates for 2007 on the weakening mortgage banking business. Earlier this year the company had provided guidance of between $7.40 and $7.80 a share, but were forced to lower these estimates today. Now the company is expecting to see between $7.00 and $7.40 for the full year 2007.

Shares of Capital One are trading down 4.8% in after hours trading, falling $3.75 down to $73.59.

Michael Fowlkes has worked as a stock trader for seven years and spent the last two years working as an analyst for the online investment advisory service Investor's Observer.

TheFly began warning in early December that poor performance at many of Motorola's (NYSE: MOT) supply chain partners -- Texas Instruments (NYSE: TXN) and National Semiconductor (NYSE: NSM) -- was likely a sign that Motorola might be set up for an earnings miss.

Late last night Motorola warned revenue and earnings would be lower than estimates. Our take: wait for the market to become oversold and more evidence that the Fed is about to lower rates and then jump in. The next growth phase in wireless will be data and Motorola is well-positioned to participate in this space.

Motorola's miss was more due to a slowing economy and a transition from the mature voice business to data. Motorola, as a company, is in pretty good shape to participate in this transition to wireless data.

When investors' fear picks up due to a slowing economy, jump back into this stock.