Amazon provided Windows AMI removed

Yes, that happens really often (to be precise every month).

The reason behind this is the application of the patching policy of Amazon provided AMIs, and Microsoft's patching policy.

Every second Tuesday of the month, Microsoft does what is commonly called a "Patch Tuesday" and release all the patches they have available for all their softwares.

We then get all the patches, select the ones that apply to our case, test and validate them, and package a new set of images (we have more than a hundred images released every month on Microsoft Windows Server).

We get the new images broadly available and listed in the wizards (usually within 5 business days of said "Patch Tuesday"), and leave the previous images available in case of need.

Finally we mark the previous images as private and customers can not access them anymore (usually 10 business days after release of the new images).

And as this happens a lot, we even have an SNS Topic that sends notifications when new images are available.

If you want to see the list of images, and the detailed process (and the steps to register to the SNS Topic), check: http://docs.aws.amazon.com/AWSEC2/latest/WindowsGuide/windows-ami-version-history.html#windows-ami-versions

If however a customer wants to keep using EXACTLY the same image he has been using before and does not want any update on this, first ask him why would he want to do that (as this is a really bad security practice), but tell him he can copy the image to his own account as a private image, and we won't touch it ever. But he will have to suffer the long startup times because of Windows Update, and will have to ensure he follows security best practices in applying the patches.