Fools, schools, and operating-system tools will lead the way in the week of earnings that lies ahead. Let's take a closer look.

Pharmacies don't seem to get a lot of love unless it's 3 a.m. and your kid is running a high fever. For Walgreen (NYSE:WAG), things are getting particularly dicey: Last month, General Motors (NYSE:GM) announced that its health-benefits plan would no longer cover prescriptions filled at Walgreen. The pharmacy chain kicks off the week with its latest earnings report, and you can bet that one of the first questions during the conference call will pry into how the company thinks it will fare without GM and whether other major companies will pull out. Companies are looking to cut costs these days, and there's nothing that can be prescribed, or even bought over the counter, that will cure that type of malady for Walgreen.

Only a few years ago, for-profit education was one of the hottest business sectors. When companies like Apollo Group (NASDAQ:APOL) were retooling and reschooling their workforce -- either through local campuses or with virtual classes -- these vocational centers were all the rage. Well, 2004 wasn't as kind. Apollo has held up better than the pack, but its shares are still trading lower than they were a year ago. Tuesday's glimpse into the company's quarterly numbers will help the market figure out whether Apollo is ready to move back to the head of the class. But investors should take care not to flunk their history lessons. Remember that Apollo has outperformed its peers because for every single quarter on this side of the millennium, the company has managed to beat analysts' projections at the time of the reports. Wall Street is looking for Apollo to earn $0.46 a share for its fiscal second quarter. Your best bet for a shiny apple on your desk is to peg your hopes closer to $0.47 or $0.48 a share.

How fiercely competitive are Best Buy (NYSE:BBY) and Circuit City (NYSE:CC)? Well, the consumer-electronics superstore giants are even reporting their quarterly results on the same day. But there really hasn't been much competition lately: Best Buy has grown impressively, while Circuit City has been busy spurning buyout offers from others who think they can run the company better. But Circuit City's commitment to going it alone and proving that it's the right move may help even the playing field again. At the very least, it will make Wednesday's comparison that much more weighty as Wall Street considers which company has more to offer its investors.

If the open-source splendor of Linux offered any moneymaking opportunities, Red Hat (NASDAQ:RHAT) figured it would be the one to benefit. But it hasn't quite panned out that way. The company has put up some healthy results -- including a profitable showing this past quarter on a 55% spike in sales -- but its shares have been cut in half over the past year.

Though we have taken the company to task for liberally using stock options and then attempting to mask the dilution by hitting up the balance sheet with share buybacks, Red Hat is still a company worth watching, especially if you like to see a small, gutsy company attempt to slay Mr. Softy. Red Hat continues to be profitable, and the sales growth is impressive. Now, if only it can keep those stock-option grants in check.

If you're wondering why the earnings slate is running a little dry on Friday, it may be that the First of April isn't the best time to be taken seriously with something as significant as quarterly earnings. Sure, you sometimes have a corporate announcement here or there -- as when Google (NASDAQ:GOOG) formally announced its email service last year -- but feel free to get an early start on your weekend. Just try not to get duped out there.

Want to learn more about the companies reporting earnings this week? Check out:

Until next week, I remain,

Rick Munarriz

Longtime Fool contributor Rick Munarriz does not own a red hat or a general motor. He does not own shares in any of the companies mentioned in this story. The Fool has a disclosure policy. He is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early.