REDMOND, Wash.—Demolition is afoot at Microsoft headquarters. On a recent morning visit, excavators ripped apart a complex of office buildings constructed in the 1980s, part of an effort to modernize the heart of the company’s 500-acre campus over the next three years.

The work was a fitting symbol for a company that began rebuilding itself when it appointed Satya Nadella as its new chief executive officer exactly five years ago, as of next Monday. In that time, Mr. Nadella has led a comeback by focusing on cloud computing, the strong growth of which was a highlight of the company's quarterly financial report released Wednesday afternoon (the company's stock slipped due to weak sales of its Windows operating system).

But in interviews earlier this month Microsoft executives seem determined not to jinx the company’s success, which could be fleeting.