On the desktop, I don't believe Microsoft has had significant competition for quite some time, likely back to Windows 95. In the server space, NT fought really hard against the UNIX giants of the time.
Windows’ share of the desktop market has dropped from about 95% in the late 90s to around 70% now.
Windows’ share of the desktop market has dropped from about 95% in the late 90s to around 70% now.