No surprise here: A 2.9% weekly gain for the OMX Stockholm 30 (INDEX: ^OMX) was spurred on by the massive gains in Nokia (NOK -0.41%) following its ground-shaking deal with Microsoft (MSFT 0.29%).

Though the partnership between Microsoft and Nokia may make this deal somewhat less of a surprise, Mr. Market nevertheless sent Nokia's shares soaring after it was announced that Mr. Softee is paying $7.2 billion for Nokia's mobile phone division. By the time the dust had settled at the end of the week, Nokia's shares had added an impressive 41%.

While that's undoubtedly a stellar week for Nokia shareholders from a "we are now significantly richer" perspective, the deal also poses a challenge. Specifically, when the deal closes, the company that Nokia investors own will look much different. Investors now face the question of whether they want to continue to own shares of the "new" Nokia. Earlier in the week, fellow Fool Chris Neiger mapped out just how that new Nokia hopes to continue cranking out profits for its owners.

Not just Nokia
But it wasn't just Nokia that was helping to pull up the OMX index. Fellow tech-and-telecom hardware manufacturer Ericsson (ERIC -1.70%) was also up big on the week, gaining roughly 11%. Ericsson's stock caught a tailwind from the Nokia deal early in the week, perhaps on the hope that a shakeup in the industry could help its competitive position.

Then, as the week was wrapping up, the research department at Credit Suisse gave the stock a thumbs up, upgrading it from neutral to outperform. The research note waxed optimistic on the prospects for the wireless network market and Ericsson's ability to benefit from that rebound.

Also getting a boost from a banking upgrade was Boliden. SEB AB boosted shares of the metals miner from hold to buy. As coverage on Bloomberg noted, the upgrade came from "an expected doubling of earnings from the expansion of its Garpenberg and Aitik mines."

What a drag!
While most of the OMX stocks were dancing the week away, AstraZeneca (AZN 0.37%) was having a rougher go of it. New data out from The New England Journal of Medicine didn't do much to boost investors' view on the company's diabetes drug Onglyza. While the so-called Savor study showed that the drug isn't any more dangerous than a placebo, it managed to raise questions about the bigger picture for Onglyza and other similar diabetes treatments. As Fool writer Sean Williams put it, this was diabetes drugmakers' "definitely maybe" moment.

Making matters worse for AstraZeneca this week was the fact that Danske Bank slapped the stock with a downgrade, pulling the shares down to a sell from hold.

A new week awaits
Danish investors are likely flying high after the past week. But the jubilee was driven largely by a type of blockbuster deal that we can't expect to repeat very often. So through the excitement, investors need to keep their focus where it always should be: Carefully evaluating the businesses they own. Sure, weekly stock price gains are great, but owning a high-quality company that will create compounding returns over years or even decades is far better.