Parallels has made a big splash over the years with its desktop virtualization software that allows Mac computers to run Windows software. Today, the company’s founder is stepping down as chief executive and appointing his No. 2 executive (a former Microsoft executive) as his replacement.

The change marks a new stage of maturity for the upstart company, which generates more than $100 million a year in revenues and creates strategically important software for Apple. Parallels makes software that emulates Windows so that a Mac user can use Windows programs on a Mac computer.

Birger Steen (pictured), president of Parallels, picks up the additional title of chief executive while founder Serguei Beloussov relinquishes the CEO title and moves to executive chairman and chief architect. It means that a former Microsoft executive is now in charge of the software that gets people to move from Windows to Mac computers.

The company made the announcement at the Parallels Summit 2011 event in Orlando, Fla. Steen left Microsoft to join Parallels in September to take the No. 2 job and oversee sales, marketing, product management, customer support and services. During that time, Parallels launched Parallels Desktop 6 for Mac.

NPD estimates that Parallels has more than 78 percent of the market for desktop virtualization software. Revenue has been growing 50 percent a year and the company is profitable with a gross profit margin higher than 90 percent. Previously, Steen was vice president of small and medium business distribution at Microsoft. Parallels was founded in 1999 and it has more than 800 employees.