Actually all major cloud providers offer virtual machine instances in a variety of Windows and Linux versions. Google and Amazon also offer Windows based vm. Though I recommend for all algorithmic trading that is hosted on remote machines to be strategic about the physical location of the server that hosts such vm and take proximity to exchanges/matching engines into consideration.
Edit: you actually mentioned about the latter point in a later post...
I wonder, are there any that boast about low latency to the data sources ? I assume once you get up in the money you can get hosted very close to the exchange data sources.