For Windows Server instances, Google Compute Engine promises “increased uptime due to transparent maintenance, cheap and predictable block storage, and best in class Google Cloud Storage Nearline backup. Sharepoint, SQL and Exchange Server, and other Microsoft applications are also available to Compute Engine customers via the Microsoft License Mobility program.”
Other OSes supported by Google Compute Engine include CentOS, Debian, Red Hat Enterprise Linux, SUSE, Ubuntu, CoreOS, FreeBSD, openSUSE, and SELinux.
http://googlecloudplatform.blogspot.com/2015/07/Bringing-Windows-to-Google-Cloud-Platform.html