(Adds comments from Tucci interview, analyst react)

By Jim Finkle

BOSTON, July 8 (Reuters) - Business software maker VMware Inc (VMW.N: Quote, Profile, Research) issued a revenue warning that sent shares tumbling 30 percent to a historical low, and replaced its CEO, one of Silicon Valley's highest-ranking women executives.

VMware, which is facing increased competition from Microsoft Corp (MSFT.O: Quote, Profile, Research) in the market for virtualization software, said on Tuesday its board named former Microsoft executive Paul Maritz, 53, to replace Diane Greene, also 53, as chief executive with immediate effect.

Greene, who could not be reached for comment, co-founded VMware a decade ago with her husband, Mendel Rosenblum, a Stanford University computer scientist.

Board Chairman Joe Tucci, who is CEO of EMC Corp (EMC.N: Quote, Profile, Research), which owns 86 percent of VMware, told Reuters VMware's Greene was replaced because the board wanted a leader with more operational experience to take the software company to the next stage of growth.

Tucci said he had asked Greene to stay with VMware, but she declined to take on another post at the company.

"This economy is tough. We don't see it improving soon," Tucci said in a phone interview.

The poor U.S. economy was a factor behind VMware's warning on Tuesday that its 2008 revenue would be "modestly below" its previous forecast of 50 percent growth over 2007, he said.