Michael Sinneck, the head Microsoft's services unit, is leaving to pursue opportunities outside of the company.
Sinneck was appointed in January 2002 to lead the services group, which includes Microsoft Consulting Services, Product Support Services and Premiere Services, as well as other services specifically for large customers.
As corporate vice president of worldwide services, Sinneck also headed efforts to improve Microsoft's partner relationships, according to Microsoft.
At IBM, where he worked for 32 years, his most recent role was as vice president of business operations for IBM Global Services Americas.
Rick Devenuti, Microsoft's chief information officer and vice president of global operations and technology, will add the services group to his responsibilities.
Sinneck is one of several recent high-profile departures and appointments at Microsoft.
Joe Eschbach, corporate vice president of its Information Worker Product Management Group, announced he would leave Microsoft on 1 December. He joined the company only a year ago from Adobe Systems.
Barbara Gordon, formerly vice president of the global sales organisation at Sun Microsystems, replaced Jonathan Murray as vice president of global accounts.
Murray was named "national technology officer", a sales and evangelism role targeted at the European public sector.
Joris Evers writes for IDG News Service