When it comes to investing, I guess you could say that currency fluctuations are a bit like earthquakes: Even if you're aware of their potential to do damage, it's hard to get worked up about them until you actually feel the impact. But with the euro having plunged and expectations growing that the Chinese government will allow the yuan to move higher relative to the dollar, this is a pretty good time for investors to take a look at their portfolios and figure out which companies are at risk of announcing weaker-than-expected because of "currency impacts."

And this definitely applies for tech investors, considering how many major tech names are dependent on European exports and/or low-cost Chinese manufacturing. A weakening euro means that these exports are now more expensive for European consumers and businesses, and that any sales carried out in euros will have a smaller impact on the company's bottom line, when measured in dollars. Meanwhile, a rising yuan translates into higher manufacturing costs for everything from MP3 players to wireless routers, thereby denting the gross margins of tech companies, and possibly (if they try to pass the higher costs onto customers) their sales.

To make matters worse, the earnings of many American companies saw a positive impact from currency trends during the first quarter, due to the dollar's weakness for much of 2009. Thus, a negative currency impact on upcoming earnings reports will be especially harsh on sequential and (eventually) annual comparisons.

Which tech stocks are particularly at risk of seeing their earnings dented by currency shifts? Here are some high-profile names that I think are worth keeping an eye on:

  • Hewlett-Packard (NYSE: HPQ). 38% of HP's revenues last quarter came from what it calls the EMEA (Europe, Middle East, and Africa) region. In addition, HP relies heavily on Chinese plants for the manufacturing of its PCs. Considering that HP's PC division only had a 4.7% operating margin last quarter, the impact of a meaningfully higher Yuan on the division's profits won't be pretty.
  • Nokia (NYSE: NOK). 32.8% of Nokia's "Devices and Services" revenue (mostly mobile phone sales) came from Europe in the first quarter, as did 39.2% of revenues for its Nokia Siemens networking equipment joint venture. What's more, with Nokia having very little market share in the U.S. and Japan, it's safe to assume that a disproportionate chunk of the company's high-margin phone sales come from wealthy Eurozone countries. The company also relies quite a bit on Chinese plants for manufacturing lower-margin devices.
  • Google (Nasdaq: GOOG). "International revenue" accounted for 53% of Google's top line in the first quarter. Considering the company's relatively weak positions in China and Japan, the Eurozone undoubtedly makes up a large percentage of this number. Oppenheimer analyst Jason Helfstein recently estimated a 3% impact on sales from currency effects next quarter, and a 10% impact during the second half of the year.
  • Amazon.com (Nasdaq: AMZN). Amazon's International segment (excludes North America) accounted for 47% of its first quarter revenues, with Eurozone sales accounting for a big chunk of that revenue figure. In addition, Amazon, like nearly every major retailer, sells plenty of merchandise with the words "Made in China" stamped on it. A rise in Chinese manufacturing costs for Amazon's suppliers will probably hurt margins and sales in both the U.S. and abroad.
  • Chinese solar stocks. The global recession hit the solar industry with all the gentleness of Godzilla stomping through Tokyo, turning it into a cutthroat business where cost efficiency is often paramount. So if manufacturing costs significantly rise for Chinese solar cell and module vendors such as Suntech Power (NYSE: STP), LDK Solar (NYSE: LDK), and Trina Solar (NYSE: TSL), things could get ugly in a hurry. And what are some of the biggest export markets for these companies? Why, major Eurozone countries such as Spain, Germany, and Italy.

Think that fears of currency mayhem are overblown? Or that some other prominent tech names are also vulnerable? Feel free to comment below.

Fool contributor Eric Jhonsa has no position in any of the companies mentioned. Nokia is a Motley Fool Inside Value recommendation. Google and Suntech Power Holdings are Motley Fool Rule Breakers selections. Amazon.com is a Motley Fool Stock Advisor pick. The Fool owns shares of Google. Try any of our Foolish newsletters today, free for 30 days. The Motley Fool has a disclosure policy.