Is there any reason for Amazon EC2 to not support Vista/XP/7 images in the cloud? I know that EC2 is primarily a platform for deployment of applications, but I can't imagine that costs or difficulties would be that much higher to also include some client-side platforms. After all, these are just virtual machines, and all it takes is a basic install to make such platforms available (ok, and maybe license negotiations with Microsoft).
I work for a startup called http://LabSlice.com and people have shown interest in using the technology to share VMs of test apps with their customers. Every so often we get asked for a Win7 image, and I assume that if we get asked then surely this would've been something asked directly off Amazon to support...