Every once in a while, I like to do a very basic screen. I take a look at companies with a market cap under $15 billion, a price-to-book ratio of less than 2, and a price-to-earnings ratio of less than five. It's a screen that is prone to error, and you can usually whittle down the 1,000-plus results in minutes because of penny stocks, stocks with zero liquidity, and obscure foreign-listed entities. But there are also usually a few companies that are well-known names with surprisingly low valuations. Let's take a look at three you know and love to determine whether they're worth your attention. Value hunters, unite!

A hard drive
Few technology companies trade at a P/E of less than 5. This century has groomed us to accept lofty valuations and pay 15, 25, sometimes 300 times earnings for a hot tech stock. For a value-oriented investor, it's often too heart-wrenching to pay up for even the most promising technology or wunderkind management. But Seagate (Nasdaq: STX) has been of particular interest to value investors, as it is in one of the more understandable businesses within the umbrella of technology and trades at a well-below-industry-average 4.71 times forward earnings.

The hard-drive manufacturer has been a major win as of late for hedge-fund manager extraordinaire David Einhorn, who loaded up on the stock last year. From fiscal 2011 to 2012, EPS growth measured a staggering 450%. It wasn't totally organic growth, as the company benefited from a supply-chain disruption caused by the Thai floods last year. Competitor Western Digital (Nasdaq: WDC) was unable to meet demand, allowing for Seagate to pick up the slack and sell more units at full retail prices.

Though the company is still relatively cheap, there are a few things to keep an eye on before making an investment. For one, Western Digital has recovered from the supply-chain issue and is steadily taking back market share lost over the past 12 months. The 450% EPS gains are not expected to repeat anytime soon. In addition, solid-state drives are coming down fast in price, as technology always does. This will, as management mentioned, cut into the fat margins the company has been enjoying up to this point.

Seagate is cheap on the surface, but a murky future for the company and the fact that the stock has already made substantial gains year over year would keep me from diving in any time soon.

Seriously
One of the most heavily followed companies on the Fool is also a cheap trade -- Sirius XM Radio (Nasdaq: SIRI). This company needs no introduction; we know exactly what it does. Now, the reason Sirius showed up on the screen was that trailing numbers have the company trading at about 4.7 times earnings. On a forward basis, it is much more richly valued at 25 times earnings.

Sirius is a difficult stock to assess at the moment. The impending-but-not-quite-yet takeover from Liberty Media (Nasdaq: LMCA) has helped the stock tick up over $2 and slither toward $3, even though shareholders and management are against the takeover. I believe Liberty's ownership could only help the company, as John Malone isn't known to be a corporate raider, but more of a horizontal integrator. His media empire has been hand-picked and has performed phenomenally -- with stakes in Discovery, Starz, and other high performers.

Challenges for the company include rising content costs and competition from Internet-based radio. It's also often said that the company is too well followed for the market to hold any inefficiencies in its pricing. The latter is the strongest argument, in my mind, against investing in the stock.

To me, Sirius is a good company as a standalone or as a takeover target. Similar to Seagate, it's enjoyed a nice run this year and isn't quite as cheap as we'd like it to be. But it's certainly still worth a look if you want a low-P/E tech in your portfolio.

For profit (or not) education
A sector that nearly all of Wall Street used to love has fallen on tough times. For-profit educators have been accused of loading up students with debt with no clear avenue to a career (I'm not sure nonprofit post-secondaries circumvent this issue) and not providing an education that's on par with its nonprofit competitors.

On the whole, I'm not a fan of for-profit education. Beyond the moral implications, it has just been a lousy business to be in the past few years.

Bridgepoint Education (NYSE: BPI) is no exception. The company has been slammed with class action lawsuits claiming the previous points and more. Bridgepoint operates Ashford University, University of the Rockies, and online education programs. It trades at a dirt cheap 4.29 times forward earnings. Keep in mind -- this valuation is indicative of how undesirable the business is.

Bridgepoint should probably be viewed as a riskier investment, if anything. The legal difficulties facing the company and the lousy industry climate will keep most investors out. But deep value hunters may like the recent 50% dip the stock price took while revenue has more than doubled since 2009. In the same time, operating income has more than tripled.

If the legal issues are resolved anytime soon, the favorable income statement may shine through and cause a nice rebound in stock price over the next year or two. I would keep a close eye on this story and consider it a contrarian play.

As always, do your homework before getting anywhere near a priced-for-doom company. I believe the market is inefficient, but it can always catch us sleeping if we aren't careful.

To extend your research and understand the opportunities and risks ahead for Sirius XM, try our recent premium report. A year of updates is also included with the report. Check it out now.