Guest Support

http://www.linux-kvm.org/page/Guest_Support_Status
Windows 2k, XP, Server 2k3, Server 2k8, 7, 2k8 R2
RHEL{3,4,5}, Fedora, Slackware, Debian, Ubuntu, Arch Linux, openSUSE, Crux
OpenBSD, NetBSD, FreeBSD, DragonFly BSD
Solaris, Nexenta, QNX
even HURD and Android :)