If Adobe is too ambitious of an acquisition at its present $22 billion-plus market cap, Tim Armstrong-led AOL ( AOL) could be an alternative worth considering.

In the 1990s a merger of Microsoft and AOL would likely have given the U.S. attorney general cardiac arrest. However, the decline of AOL's dial-up Internet business and Microsoft's perennial underachievement in Web search mean both firms aren't the tech sector monopolists they once were.

AOL would bring Microsoft significantly less congruous or important assets as Adobe; however, the company's CEO Tim Armstrong has proven himself as among the savviest turnaround experts in American business. In fact, Microsoft presently has many issues such as a declining legacy business that Armstrong has been effective at resolving at AOL.

As AOL's dial-up Internet business continues to move towards extinction, Armstrong has sold non-core intellectual property assets and reinvested in businesses that could propel the company forward in coming years. While profits from popular media brands such as Huffington Post, Techcrunch and Patch.com are uncertain and likely immaterial to Microsoft's earnings, they could be helpful to the company if it plans to be in the consumer mobile markets for the long haul.

Armstrong has proven he has the financial discipline that will be a part of Ballmer's legacy at Microsoft, and he also has shown a decisiveness and vision that is much needed at the top of the software giant.

Of course, Microsoft could decide that Ballmer's biggest failure was his obsession with chasing consumer markets.

Ballmer plowed billions into Zune to compete against the iPod, he was unable to capitalize on an early lead in the smartphone market and then didn't deliver on the Windows Phone or Windows 8. Xbox stands out as one of the rare areas where Microsoft has seen success in a consumer facing business.

The company could try to spin off its smartphone, tablet and console businesses and reinvest in faster growing enterprise markets such as cloud computing.

Salesforce.com ( CRM) and its CEO Marc Benioff could be a nice fit for Microsoft and help it regain its mystique as a force to be reckoned with. While Salesforce.com has struggled in recent quarters, the company nevertheless has businesses that would revamp Microsoft's offering to enterprise customers.

Such a move would likely strike fear in competitors such as IBM ( IBM) and Oracle ( ORCL) -- now a partner of Salesforce.com - and signal that the company won't allow for a terminal decline of its desktop software businesses.

There are many other companies and CEOs who could add much needed assets and vision to Microsoft. What is clear is that Microsoft will have to do far more than hire a replacement to Ballmer if it wants to continue to be considered among the tech sector's elite businesses.

-- Written by Antoine Gara in New York

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