All great recommendations, and I thought I'd add this article I found, which relates to expanding a Windows Amazon EC2 EBS instance using the Amazon Web UI tools to perform the necessary changes. If you're not comfortable using CLI, this will make your upgrade much easier.
http://www.tekgoblin.com/2012/08/27/aws-guides-how-to-resize-a-ec2-windows-ebs-volume/
Thanks to TekGoblin for posting this article.
