In the age of information, investors always want to know why their stocks are moving. Yet sometimes, especially on lackluster days like today, there aren't any obvious reasons the market moves up or down. Certainly, you can point to factors like rising Italian bond yields and concerns about their potential impact on the European financial crisis as contributing to a negative tone. But after the strong upward movement in the stock market that we've seen in recent months, today's 22-point drop in the Dow Jones Industrials (DJINDICES:^DJI) isn't terribly significant. The S&P 500 and Nasdaq Composite actually dropped even less, with a percentage loss of 0.06% each.

The Dow didn't hold back Microsoft (NASDAQ:MSFT), though, which climbed more than 1% after its Surface Pro tablet launched over the weekend. Sales were strong, although reviews were mixed, with many impressed by the functionality of having full-blown versions of popular software programs available. The question is whether, at a fairly hefty price point, customers will be willing to pony up for the tablets rather than accepting cheaper laptops as substitutes. This weekend, the answer was yes, but Microsoft needs much more than a few days of positive results to convince investors that its long drought is over.

Elsewhere, Regeneron Pharmaceuticals (NASDAQ:REGN) climbed almost 3% on news that Sanofi (NYSE:SNY) will boost its holdings of the biotech by about $500 million. With Sanofi already owning a big stake in Regeneron, the move isn't necessarily all that significant by itself. But as merger and acquisition activity has been heating up in the pharmaceutical and biotech spaces, Regeneron investors hope that macular degeneration drug Eylea will prove to be enticing enough to draw a full-out bid for the company in the near future.

Finally, SunPower (NASDAQ:SPWR) regained every bit of its 6% loss on Friday and then some, soaring 19% today. One interesting trend being talked about in the solar industry, according to the Financial Times, is the possibility of using solar-panel leases as collateral for asset-backed bonds. The hope is that by creating a more liquid market, overall demand for solar systems will rise, helping SunPower and its peers to boost their profits in what has been a tough environment for solar stocks.

Fool contributor Dan Caplinger has no position in any stocks mentioned. You can follow him on Twitter, @DanCaplinger. The Motley Fool owns shares of Microsoft. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.