A similar desktop but with their own feature. We have gnome that seems similar to Mac, KDE to Vista. A different of linux desktop screenshots to mac and Vista is a price.
Mac http://www.apple.com/ The Mac is the only computer in the world that can run all the major operating systems, including Mac OS X, Windows XP, and Vista. With software like Parallels Desktop or VMware Fusion you can even run them side by side
Gnome http://www.gnome.org/ GNOME offers an easy to understand desktop for your GNU/Linux or UNIX computer. Learn more about GNOME as a whole, get our latest release, find help and support, join our great community, start to develop with GNOME, study our Foundation, or simply get in contact with it
Windows Vista http://www.microsoft.com/ Windows Vista makes it easier, safer, and more entertaining to use your PC virtually anytime and anywhere
KDE http://www.kde.org/ KDE is an international technology team that creates Free Software for desktop and portable computing. Among KDE's products are a modern desktop system for Linux and UNIX platforms,
Mac OS 10.2
Gnome (Dreamlinux)
Microsoft Vista
KDE 4 
posted on Mar 5, 2008 12:31 PM ()