Today is the official start of earnings season, as Alcoa is set to report second-quarter earnings after the closing bell today, and investors seem confident that they'll receive strong numbers as two of the three major indexes are move higher this afternoon. As of 12:45 p.m. EDT, the Dow Jones Industrial Average (^DJI -0.98%) is up 82 points, or 0.54%, to 15,218. The S&P 500 is higher by 0.51%, and the Nasdaq is the lone loser, down a negligible 0.07%.

Only a handful of the Dow's 30 components are down for the session, and three of the Dow's big losers today can blame one Citi Group analyst for their woes. Glen Yeung changed his earnings forecast for Intel (INTC 1.77%) from $0.39 per share to $0.38. This change has caused shares of the chip maker to fall 3.8% today. Based on his figures and PC data checks, personal-computer sales are tracking worse than previously expected.

That little piece of news has sent shares of Hewlett-Packard (HPQ 0.11%) and Microsoft (MSFT -2.45%) down by 1.2% and 0.5%, respectively. As good a job as Meg Whitman has done more than 18 months into HP's turnaround, the company still relies on PC sales and will likely depend on a strong PC business for at least another year or two. So today's report from Yeung has naturally caused some downward pressure on HP's stock. As for Microsoft, the story's much the same. The company still needs its Windows software to bring home the bacon, and weak PC sales indicate that Windows may not perform as well as some have predicted.

But it's also important to note that all three of these companies have made major strides toward becoming more diverse companies with a wider range of offerings. Most importantly, they're making inroads in the mobile industry. Intel now has chips in tablets, while HP has teamed up with others to make tablets. Microsoft, of course, has the Surface tablet and the Windows 8 operating platform, which was designed to be used on mobile devices.